Online talk radio aggregator Stitcher nabbed $6 million from Benchmark Capital and will use the money to give radio blabbermouth Rush Limbaugh, as well as the endlessly talking heads of National Public Radio, even more digital distribution.

The San Francisco-based start-up often describes itself as the the Pandora of online talk radio. And like the digital music site, Stitcher lets its users create and customize their own free personalized talk/information/news radio stations.

The site focuses mostly on its apps for a variety of mobile devices, especially increasingly popular smartphones. It offers programs from about a thousand different sources, such as NPR, E! and The Onion.

Stitcher also recommends new programs to users based on their selections.

The infusion of funding in a Series B round led by Benchmark–whose partner, Bob Kagle, will have a seat Stitcher’s board–will allow it to expand its advertising sales force and improve its offerings, said CEO Noah Shanok in an interview with BoomTown last night.

“The hope for everyone in terrestrial radio is to find new audiences, so as we grow, they will too,” said Shanok, who co-founded Stitcher in 2008. “We want to be a part of everyone’s everyday life.”

Shanok said fast-growing usage and engagement–which he declined to give specifics about–was the reason Benchmark was attracted to the company.

The new funding adds to $3 million Stitcher already raised from New Atlantic Ventures and investors Ed Scott and Ron Conway, who also participated in the new round.

While the mobile app on the Apple (AAPL) iPhone is the most popular, Stitcher also offers software for Research in Motion (RIMM) BlackBerry, Palm (PALM) Pre and Google (GOOG) Android devices.

Stitcher is also pushing into other areas, such as being part of Ford’s (F) initiative to make its SYNC-enabled vehicles into Wi-Fi hotspots, allowing people to connect to the Internet everywhere much more seamlessly in a moving car. They will be available later this year.

Here’s the press release on the funding:

Stitcher Secures $6 Million in Series B Venture Funding

Benchmark Capital Leads New Round to Help Transform the Way We Listen to Talk Radio

SAN FRANCISCO, CA. (April 6, 2010)–Today, Stitcher, a service that allows users to customize talk radio programming on their mobile devices, announced that it has completed its Series B round of financing. Led by Benchmark Capital, with participation from previous investor New Atlantic Ventures and tech veterans including Ed Scott and Ron Conway, the funding will be used to further Stitcher’s product and platform development. Bob Kagle of Benchmark will join Stitcher’s board of directors.

“We know that people prefer listening to news, talk and information programming when they’re on-the-go. The rise of smartphones has finally created an opportunity to give people exactly what they want to hear–on their commute, at the gym, on a road-trip–wherever and whenever they want it and that’s exactly what Stitcher does,” said Noah Shanok, CEO of Stitcher. “Benchmark’s funding, combined with Bob’s guidance, will help us continue to take advantage of the growing market for mobile content distribution.”

Stitcher’s free service allows users to create a personalized audio programming experience. With Stitcher, users can listen to the news and talk radio shows they enjoy whenever and wherever they like, using their mobile devices. Users choose their favorite programs from more than a thousand different sources, and Stitcher then delivers the audio feeds to their phone as a single, regularly updating radio station. Stitcher also helps users discover new content on a variety of topics–including business, sports, politics, entertainment, and current events–by recommending additional programs based on the shows users have in their feeds. A single radio station can include programming as diverse as Fox Headline News, NPR’s Fresh Air, TechCrunch Headlines, Onion Radio News, and E!’s Hollywood Rap Up.

“Stitcher is transforming the way we all consume news, talk radio, pod casts,” said Bob Kagle, general partner at Benchmark Capital. “Noah and his team are building a platform that will deliver the personalized experience consumers currently enjoy for music to the broader world of audio programming. We’re thrilled to join the Stitcher revolution.”

Here’s the list of publishers Apple (AAPL) says “deliver content that looks and functions beautifully on iPad”:

CNN
Reuters
New York Times
Vimeo
Time
Major League Baseball
The White House
Virgin America
Sports Illustrated
Flickr
People
TED

Apple acknowledges that this isn’t a complete list of iPad-compatible sites–both NPR and The Wall Street Journal, for instance, are overhauling their pages for the gadget–and it’s unclear whether Apple has any criteria for calling out these sites in particular. (For the record, I’m told that All Things Digital should work just fine, too).

But for whatever reason, the list appears to be particularly heavy on sites owned by Time Warner (TWX). CNN makes the cut, as do Time Inc. magazines Time, People and Sports Illustrated.

One other note: Check out the description Apple uses for each of the sites it calls out and you’ll see that “iPad-compatible” doesn’t mean “completely free of Flash.”

In many cases, Apple can’t say that all of the sites’ videos will play on the gadget. Just “most” videos, or “recently published” ones.

So here’s one that just started running: A campaign for AMC’s “Breaking Bad” series that’s running on iPhone apps for CNN and NPR.

The video below should give you some clue about how the ad, produced by mobile marketing start-up Medialets, works. But in case you can’t tell, the idea is that you click on a small banner ad, which turns into a mini-app that lets you “mix your own chemicals” and eventually lets you watch a trailer for the series (about a chemistry teacher turned meth dealer) or buy an episode via Apple’s (AAPL) iTunes.

If you follow mobile marketing, this might seem familiar. Last year, Medialets rolled out a campaign for Dockers that asked users to shake the ads. And earlier this year, the firm rolled out a campaign for Vampire Weekend’s new album that asked users to shake the ads. At some point, the novelty factor for this stuff will wear off.

Meantime, it’s still going to be new for most users. If you’re really into this stuff and you live in New York, stop by Apple’s Soho store Friday, where the show’s creator will be promoting the show and the app ads.

But the standoff between Apple (AAPL) and Adobe has prompted NPR to take on another engineering project at the same time: It is building a version of its Web site designed specifically for the iPad.

So if all goes as planned, iPad users who want to listen to NPR programming will have a couple choices next month. They can:

• Download a free iPad-optimized version of the broadcaster’s popular (two million downloads) iPhone app. Or
• Use the iPad’s browser to visit NPR.org, which will detect that it’s being viewed with Apple’s device and serve up a custom-built site. This means no trace of Adobe’s (ADBE) Flash, which is used to power graphics and media on the site.

I’ve heard about a handful of other big publishers who are altering some but not all of their Web sites to create iPad-optimized versions.

That’s what The Wall Street Journal–like this Web site, the Journal is owned by News Corp. (NWS)–is doing, for instance: Visitors to the newspaper’s front page will see an iPad-specific, Flash-free page. But those who click deeper into the site will eventually find pages that haven’t been converted.

Kinsey Wilson, who oversees digital media for NPR, says he has been able to create a new version of his Web site–while keeping the existing one up and running for other visitors–because of the site recent redesign, which split up the data that powers the site from its presentation layer. In English, this means NPR can swap out the site’s facade while keeping its plumbing and foundation intact.

Just as important: NPR only runs a smattering of advertising, in the form of sponsorships it sells to a handful of marketers. This means it doesn’t have to worry about how to handle the Web ad ecosystem, which depends on Flash. Wilson says NPR has locked up a launch sponsor for both the iPad app and the custom site.

So what will the app and site look like? Alas, NPR won’t let me see a demo or look at mock-ups, i part, I gather, because the network is still building the things.

But here’s something to chew on until launch: Wilson says that while iPhone apps are a “very intentional experience”–you load the thing up and seek out specific content–he thinks the iPad will be a “lean back device.” That’s traditionally the distinction multimedia types use to differentiate between a computer and a TV. Intriguing.

The trusty radio has finally received an upgrade—to the world of high definition. HD Radio, which has been gathering steam for a few years, sounds better and offers more channels than traditional radio. It also sends properly equipped devices text data like a song’s title and artist name as well as traffic, weather and stock information. One HD Radio even lets you pause programming in mid-stream, so you don’t have to miss a song or NPR story just because you’re drying your hair. And future HD Radio devices will record programming like television DVRs do now.

The Sony (above) and Coby Electronics (below) devices use HD Radio technology to play more stations at better sound quality.

This week, I tested three HD Radio devices to see what all the hype was about: Best Buy’s Insignia $50 HD Radio Portable Player (http://bit.ly/75FcIc); Coby Electronics Corp.’s $100 Portable HD Radio System (http://bit.ly/6G6g4Q); and Sony’s $160 HD Radio with Dock for iPod + iPhone (http://bit.ly/8c0Bqf). I also talked with iBiquity Digital Corp., the company that developed HD Radio technology and licenses it to broadcasters and radio manufacturers, about how this works.

I found some worthwhile offerings in HD Radio, like commercial-free, sub-channels within existing stations and better sound quality. IBiquity claims that HD Radio makes FM stations sound like CD quality and AM stations sound like FM; to my ear, this seemed to be true.

Overall, I didn’t hear enough incredibly great content or sound quality to want to run out and replace my old radios. Washington, D.C., where I live, supposedly offers 41 HD Radio channels, but I couldn’t find as many as that. Over 2,000 primary HD Radio stations and some 1,100 sub-channels can be heard in all 50 states and Puerto Rico, but some areas won’t offer as many stations, according to iBiquity.

Tuning in each HD station takes longer, like the way changing channels on a digital TV takes an extra second. But in my tests, this process took five seconds or more per change of channel. This kind of delay is enough to try anyone’s patience.

It might help to explain the technology behind HD Radio. HD Radio makes it possible for local broadcasters to transmit content via digital signals on existing AM and FM frequencies. The digital signals are encrypted and eliminate static heard in analog broadcasts, resulting in better sound quality. But they take longer to be decoded by HD Radio receivers.

Many people mistakenly think that in order to listen to HD Radio, they must pay an extra monthly fee like with satellite radio. If you buy an HD Radio device, you’ll only pay for it because the service itself is free; its price is built into the cost of the hardware.

Besides boosting the signal, HD Radio offers extra channels of programming you wouldn’t hear on a regular set. It allows existing FM channels to play additional content on “multicast” channels. Most multicast channels are commercial-free, and they appear on the radio’s display as HD2 and HD3.

Don’t confuse HD Radio with the text data that scrolls across the screens of many current radios, like my car radio. This is a non-audio service called Radio Broadcast Data System that has been around for a while.

Each of the radios I tested offered an HD Seek feature—a way of skimming through all stations to find and play those that could be heard in HD. But HD Seek didn’t stop on multicast channels; to get to those on each radio, I had to press buttons to tune up or down while listeningwhile already listening to to a main HD radio channel. Some HD Radio models have HD Seek tuning functions that find HD1 stations as well as HD2 and HD3 channels. I saved these HD2 and HD3 multicast channels in my radio presets so they were easier to find again.

While a radio was tuning in, or linking into, a channel (the process that took several seconds), an “HD” logo flashed on each radio’s display. This logo turned solid when the station was found and finally started playing. I listened to multicast channels like a bluegrass/country station from my local NPR channel. Another station’s two multicast channels played “South Asian” music and the Mormon Channel.

As its name suggests, Sony’s HD Radio with Dock for iPod + iPhone has a built-in dock for iPods, iPhones and iPod Touches. If, while using this radio, you hear a song on an HD channel that you like, you can hit a “Tag” button to save information about that song. The next time you dock an iPod, iPhone or iPod Touch into the Sony radio, these tags are transferred onto the portable player. When you plug that device into a computer and open the iTunes Store, a list of the tagged songs appears, making it easier to recall songs you liked and may want to buy. This radio is a tabletop model and has the largest display screen of the three radios I tested. It also comes with a remote. It saves up to 20 FM and 20 AM presets.

The Insignia HD Radio Portable Player is a much smaller unit that comes with earbuds and an armband for exercising. If this radio tuned in an HD channel that offered multicast sub-channels, these were indicated on the display with a “+” sign, like “HD1+.” The Insignia radio stores 10 preset stations.

The Coby Electronics Portable HD Radio System resembled a single, lightweight speaker with a wheel, six buttons and a digital display on it. IBiquity Digital said this model uses an older HD Radio technology that doesn’t offer as much reception sensitivity as the Sony and Insignia. Still, it was simple to use, and its wheel made it a cinch to tune in HD2 and HD3 channels. It stores up to 10 presets.

In September, when Microsoft’s Zune HD was released, I tested its built-in HD Radio, the only such device capable of pausing live radio content. I paused music and talk radio on the Zune’s HD Radio when my phone rang, then un-paused the station to resume. This doesn’t work if the device is turned off and on again before resuming play.

Along with stand-alone radios, HD Radio receivers also are becoming more common in home audio systems and in cars. But while HD Radio’s sound quality and extra channels are definite pluses, the number of available stations needs to improve to make the wait for the HD channels to start playing more tolerable.

Edited by Walter S. Mossberg.

Write to Katherine Boehret at mossbergsolution@wsj.com