Caryn Marooney (pictured here), the co-founder of one of Silicon Valley’s premier tech communications firms, OutCast Agency, is joining Facebook to lead its tech public relations strategy.

Facebook said Marooney is joining the social networking giant in a newly created position as director of technology communications.

That means she will be in charge of outreach to the technical community, Facebook said, including “our product, platform, infrastructure, and technical recruiting communications–to reach developers, engineers, technology influencers and bloggers who write about our products and technology strategy.”

“Caryn’s experience extends beyond technology communications and I’m delighted that we’ll all have the opportunity to draw on her wisdom and insight,” said Facebook global communications chieftain Elliot Schrage.

Marooney has actually led the Facebook account for OutCast, which she and Margit Wennmachers built and sold to Next Fifteen Communications Group in 2005 for over $10 million.

Marooney said in an interview today that she felt the firm was in good hands with its current team of top managers.

“The opportunity at Facebook was too good to pass up,” she said. “It’s an exciting new challenge.”

Indeed, the social networking giant is preparing to go public within the next year and will need an even stronger PR team for that task.

Marooney follows Wennmachers to a company they served as outside communications advisers. Wennmachers joined the high-profile Andreessen Horowitz venture firm last year to work on marketing strategies with companies in which it invested.

Margit Wennmachers (pictured here), one of Silicon Valley’s leading public relations and communications execs, is joining Andreessen Horowitz as a partner.

Wennmachers, 45, co-founded OutCast Communications, whose clients include Yahoo (YHOO), Facebook and Andreessen Horowitz.

The move will make her one of a handful of women at high-profile venture outfits.

At Andreessen Horowitz, she’ll focus on bringing marketing expertise to the firm and its portfolio companies, starting in September.

“For me, it’s a chance to build a top-notch VC firm and work with talented entrepreneurs, so what’s not to like?” wrote Wennmachers in an email to BoomTown (who got off a horse in Wyoming to write this).

Andreessen Horowitz has made a big splash since it was created a year ago with $300 million in funding. Its portfolio of high-profile companies includes Skype, RockMelt and Zynga.

Wennmachers got to know both Marc Andreessen and Ben Horowitz when they hired OutCast to launch their firm last year. Andreessen Horowitz will continue to be an OutCast client.

OutCast was founded 13 years ago by Wennmachers and Caryn Marooney. It was bought by Next Fifteen Communications in 2005, but has been operated independently ever since and will continue to be.

In fact, Marooney will continue to run OutCast, which has more than 80 employees in San Francisco and New York.

Its clients reflect a breadth of Web and other companies–big and small, public and private–also including AdMob, Aliph, Amazon (AMZN), Autodesk (ADSK), Bloom, VMware (VMW), salesforce.com (CRM), Code Advisors, Cisco (CSCO), Zimbra and Netflix (NFLX).

“OutCast is the best in the business. Between VMware, salesforce.com and Facebook, they have an outstanding track record of working with the best companies and making them more valuable,” said Andreessen. “We are thrilled that one of the founders has decided to join our firm. Margit’s experience in building brands will be a big asset to Andreessen Horowitz and our portfolio.”

Gas prices through the roof?

Mortgage crisis continues?

A looming recession?

You almost have to admire Web 2.0′s fight for their right to party.

Last night, it was quite a festive mood, as a mess o’ tech press and a bunch of digital movers and shakers showed up at OutCast Communications’ Seventh Annual CEO Dinner, held in the Grand Hall of San Francisco’s historic Ferry Building.

Big clients of OutCast include Facebook and Yahoo, as well as a lot of hyper-trendy start-ups.

Here is a lovely video I did, featuring OutCast’s T.J. Snyder and Margit Wennmachers, investor Ron “Sister Woman” Conway, Yahoo (YHOO) communications czar Brad Garlinghouse and PR’s Nicki Dugan, Facebook’s Brandee Barker, VC Stewart Alsop and the incomprehensibly iPhone-addled Robert Scoble: