Today’s addition, which is one of dozens of native apps available in the Kindle Store, is from a small Redmond, Wash.-based start-up, which has built Wordoku, a spin on Sudoku, that uses letters instead of numbers, and acts just like puzzle books found in airports, drugstores and bookstores. The application will cost $3.99, much like other games available in the store.

While it’s easy to dismiss the release as just another game for the Kindle, Roy Leban, CTO and founder of Puzzazz, sees it as much more and has ambitions to change the kind of applications that are built for the Kindle. In all seriousness, he says: “This is big. People will look back at this and really see this as a big change in puzzle delivery.” It’s being called the first in a series of ActiveBooks for Kindle.

The app is the first one that Puzzazz has built, and has taken priority over other more robust developer platforms, like the iPad or other smartphones. Puzzazz has five employees and is self-funded. Leban takes no salary and does consulting on the side to support his habit.

As a true puzzle enthusiast, who’s been published in the New York Times and has been a part of eight previous tech start-ups, Leban is easygoing and entertaining, and puts you on the spot by asking you riddles. In one such example, the clue is “Cape horn?,” 8 letters.” (See bottom of post for answer.)

He claims he can breathe new life into the Kindle games. Some of the other titles that have been produced in the beta program are Electronic Arts’ Sudoku and Solitaire, and there are also four additional titles that have been developed by Amazon, like Blackjack and Minesweeper. But clearly they are all repositioned games from other platforms.

Leban claims the approach is wrong. The Kindle is fundamentally not a gaming platform–it’s an e-reader.

To that end, he doesn’t call his new title a game–it’s a puzzle book. It works in the same way as other puzzle books. You can start one puzzle and not finish it. Then move on to the next page and come back later to take a stab at the first one again. Users can change the difficulty after buying the book that fits their needs; otherwise, the puzzles get slightly more difficult as you work your way through the 100-page book.

That’s unlike EA’s offerings, because you have to start a new game and can’t return to multiple puzzles once you’ve left the screen.

To achieve this, Leban says, the puzzles aren’t computer generated, but rather developed by humans with the help of some algorithms. While the differences may be perceived as slight, he says it’s a quality standard that a Saturday New York Times puzzle solver could appreciate compared with the easy puzzles found in drugstores.

But could his idea be even bigger than this?

That’s his hope.

Kindles, iPads and other emerging tablet devices are also expecting to deliver college textbooks, which today are much like scanned pages of a PDF. Why couldn’t a textbook be more interactive?

Students could solve math problems in the same paragraph that introduces the concept, and if their answers are incorrect, they could be instructed on where they went wrong. “The publishing world is so old-school and they don’t have imaginations. They need a kick and we think we serve as a kick.”

As for whether the Kindle will be a big platform for third-party apps, it’s hardly comparable to Apple’s developer community or approval process for the iPhone or iPad. According to the KindlePost.com blog, it’s been announcing three new games for the past two months.

With no numbers on how well the Kindle is selling, or how well the games on the Kindle are selling, it’s unclear what Leban’s real opportunity is, other than getting the standard 70 percent cut of each puzzle book he sells. The Kindle developer program is in beta, which occasionally releases titles to the Kindle Store. A few games have been highlighted in the Kindle blog.

Riddle from above: First clue is “Cape horn?” (8 letters), additional clue is “Horn of South Africa,” third clue is “World Cup noisemaker.” Answer: Vuvuzela.

Top 10 Paid iPad Apps

1. Pages
2. GoodReader for iPad
3. Numbers
4. Angry Birds HD
5. Keynote
6. Glee Karaoke
7. WolframAlpha
8. Pinball HD
9. Friendly for Facebook
10. Star Walk for iPad

Top 10 Free iPad Apps

1. iBooks
2. Pandora Radio
3. Netflix
4. Google Mobile App
5. Solitaire
6. Movies by Flixster–with Rotten Tomatoes
7. IMDb Movies & TV
8. Kindle
9. Google Earth
10. Virtuoso Piano Free 2 HD

Top 10 Grossing iPad Apps

1. Pages
2. Numbers
3. Keynote
4. LogMeIn Ignition
5. SCRABBLE for iPad
6. Documents To Go® Premium–Office Suite
7. Angry Birds HD
8. Real Racing HD
9. Plants vs. Zombies HD
10. Proloquo2Go

Top 10 Paid iPhone Apps

1. Angry Birds
2. Doodle Jump
3. Skee-Ball
4. Bejeweled 2 + Blitz
5. Fruit Ninja
6. Cut the Rope
7. ALL-IN-1 GAMEBOX
8. The Moron Test
9. Plants vs. Zombies
10. Pocket God

Top 10 Free iPhone Apps

1. Facebook
2. Angry Birds Lite
3. Words With Friends Free
4. Skype
5. Tap Tap Revenge 3
6. The Weather Channel®
7. Paper Toss
8. Bing
9. ROCK BAND FREE
10. Talking Tom Cat

Top 10 Grossing iPhone Apps

1. MLB.com At Bat 2010
2. Angry Birds
3. Call of Duty: Zombies
4. Bejeweled 2 + Blitz
5. FriendCaller 3 Pro
6. Zombie Farm
7. TomTom U.S.A.
8. TETRIS®
9. Plants vs. Zombies
10. Doodle Jump

Scrabble is just one of the many ‘apps’ available for the iPhone and iPod Touch.

In just the first 10 days since the new iPhone and the App Store launched on July 11, more than 900 programs — applications, or “apps,” in tech jargon — have been introduced by numerous developers. Over 90% cost less than $10 or are free.

Even more noteworthy: iPhone and Touch users have downloaded 25 million copies of these programs, ranging from silly sound effects to challenging games; from news readers to restaurant locators; from social-networking programs to business applications.

We have been furiously downloading and trying out scores of these programs, using a new iPhone 3G, an original iPhone and an iPod Touch, and in general, we are very impressed. We found the process of choosing and downloading apps to be easy and quick, and most of the programs to be useful or entertaining. The vast majority are nicely designed, with great graphics and effective, simple user interfaces.

The easy availability of so many programs written by developers beyond Apple (AAPL) itself makes the iPhone a true computing platform, like a pocket-sized Windows or Macintosh PC. With so many programs already available, and many more in the pipeline, iPhone and Touch owners can have a device with fresh, different capabilities every day.

But the process isn’t perfect. For one thing, it is controlled by Apple, which can theoretically bar a program from distribution or take its time making one available.

There are also some glitches. If you download a lot of apps in a short period, it can slow the phone’s next synchronization with iTunes to a crawl, while iTunes tries to back up all the new programs, each of which can contain numerous hidden files. And there’s a bug in the new iPhone operating system that causes apps to crash, and can even force the iPhone or Touch to reboot, if you use a large number of the new apps in quick succession. Apple says it is working on fixing the latter problem.

Also, Apple’s claim of over 900 programs is somewhat misleading, because more than 100 of those are individual books you can read on the phone.

Apple’s baby isn’t the first smart phone that has attracted developers. Thousands of third-party programs already exist for Nokia (NOK) phones, BlackBerrys, and phones running the Palm (PALM) and Windows Mobile operating systems. But, compared with the graphically rich, snappy iPhone apps — many of which fetch data from the Internet at high speed — the typical program on these older platforms looks positively primitive.

AOL’s AIM program

The App Store can be accessed either from the device itself or from Apple’s iTunes software on a Windows or Mac computer, which then transfers the app to the iPhone or Touch. The programs cover a wide range.

Some fill in obvious holes in Apple’s original complement of iPhone software, things the iPhone has lacked that other phones have. These include AOL (TWX) Instant Messenger, a variety of task and to-do lists, sophisticated note takers and a voice dialer. There are numerous versions of popular board, card and word games, like solitaire, mahjong, Scrabble and Sudoku. There are also eye-popping iPhone versions of popular video games, some controlled by the phone’s motion detectors, which allow you to move cars and characters by just tilting the phone.

Numerous programs let you perform Internet functions without using the Web browser on the iPhone or iPod Touch. These include news readers, Internet radio players, sports-information apps, and programs that let you blog or use Google (GOOG) or Facebook or MySpace.

There are business programs from Oracle (ORCL), Salesforce.com and Bloomberg. And there’s a clutch of Bible programs.

Some are simply goofy, like a virtual Star Wars-like lightsaber, a rotary-phone dialer and a virtual “stapler.” And several programs turn the phone into a flashlight for emergencies.

There are way too many interesting apps to review here, but these are some we liked, in no particular order.

AOL Radio

AIM: free

This version of AOL’s popular instant-messaging program does a competent job with text chat, though it can’t yet do video or audio chats, or transfer files. Because Apple isn’t allowing third-party programs to run constantly in the background, you can’t receive new messages in AIM while doing other things. This will supposedly be fixed by new Apple technology due later this year.

AOL Radio: free

While the iPhone and Touch contain full, terrific iPod capabilities, they don’t come with Internet radio players like this one. It can stream music and talk from a wide variety of online sources, including the Internet versions of broadcast radio stations.

Evernote: free

This is an elegant note-taker that has been on computers for a while. You can jot down text notes, store photos or dictate audio memos. And it synchronizes with your Evernote account on Windows or Mac PCs or the Web.

Instapaper: free

A handy way to store Web pages on your iPhone or Touch for reading when you’re offline. While on your computer, an Instapaper button added to the Web browser can snag Web pages for your personal Instapaper database. Then, when your iPhone or iPod Touch is online, it synchronizes with the Web-based Instapaper database. Later, when you’re offline, the pages are still there on the device, ready to read.

Travelocity TravelTools: free

You can use this to check flight schedules, gate assignments and security waiting times. While you can’t book flights through this app, there’s a button that automatically calls Travelocity’s toll-free booking line.

More Cowbell!: free

This is inspired by the Christopher Walken/Will Ferrell Saturday Night Live skit, which made the lowly cowbell a cult musical instrument. Whenever you tap the on-screen cowbell, it makes the recognizable, hollow sound heard in songs like “Down on the Corner,” by Creedence Clearwater Revival. You can play along with any song you choose on the iPod Touch or iPhone.

Touch Tarot: $0.99

Touch Tarot

Touch Tarot is a digital tarot-card reading that takes place on your iPod Touch or iPhone, instead of at a table inside an incense-scented tent at the county fair. Phrasing above each card tells its general category, and below each card is a brief explanation of its meaning. For example, we turned over the Wheel of Fortune card in one card reading, and it said, “Advancement for good or ill. The unexpected may occur. Good fortune.”

iWant: free

The iWant app displays 12 black-and-white icons on your device’s screen, each representing a different category of something you might be looking for — including restaurants, bars, cafés, hotels, drugstores, banks, car rentals and movies, among others. The device identifies your location, and each category can be tweaked to search by distance or highest rankings from Yelp, a user-written rating service.

Urbanspoon: free

Urbanspoon resembles a slot machine: From left to right, columns show the location, cuisine and cost of nearby restaurants. Instead of pulling a lever to start the slot machine, you simply shake your iPhone or iPod Touch whenever you want to find a restaurant. When it stops, you see the name of a restaurant near you and its classification in each category. (You can also specify what location, cuisine or cost you’re looking for.)

Air Hockey: $0.99

Air hockey works like the game you used to play in your best friend’s basement. You play against the computer, using a fingertip to push red or blue mallets that move a puck around the screen-turned-table and trying to sneak the puck past your computer opponent to score a goal.

MotionX Poker: $4.99

MotionX Poker

This is an addictive poker game, played with realistic, beautifully rendered dice instead of cards. The cool thing is that you roll the dice by simply shaking the iPhone or iPod Touch; convincing sound effects accompany each roll of the dice.

MLB.com At Bat: $4.99

There are lots of cellphone apps and services that can give you live updates on baseball games. What’s special about this one is that it adds video clips of key plays that you can view while the games are still in progress, using the full power of the gorgeous screen and video player on the iPhone and the Touch.

Crash Bandicoot Nitro Kart 3D: $9.99

This is a rollicking, fun iPhone and iPod Touch rendition of the classic video racing game, where you control your car by tilting the phone. The graphics are good, and the game-play is responsive.

Truphone: free

This is the first app for the iPhone that allows you to make cheap phone calls over the Internet instead of using the built-in cellphone capability, which can be much costlier, especially for international calls. In our tests, we had some trouble at first, but after we removed and re-installed the program, it worked fine. Calls to 40 countries are six cents a minute to landlines and 30 cents a minute to cellphones. The iPod Touch lacks a microphone, so this app works only on the iPhone.

Write to Walt and Katie at mossbergsolution@wsj.com