Sean Parker is no stranger to Internet success. He’s 28 years old and has already helped start four very well-known services on the web: Napster, Plaxo, Causes, and of course, Facebook. And now he’s taking his impressive resume to Yammer, where he is joining the enterprise microblogging service’s Board of Directors, we’ve learned.

Yammer, which won the top prize at last year’s TechCrunch50, recently rolled out a bunch of updates to its web version, as well as its Adobe Air-based desktop client. We use the service on a daily basis for work, and those of us with iPhones are all eagerly awaiting the release of the new version of the iPhone app with Push Notifications.

As the core concepts behind Yammer are quickly becoming features that others in the enterprise space are realizing they will need to compete with, Parker’s guidance should help the company maintain an advantage, and push forward.

Parker is currently serving as the Chairman of Causes, one of the most popular social networking applications, and is a Managing Partner at the VC firm, Founder’s Fund. He is perhaps best known for serving as Facebook’s President during the time it was founded. That role is about to get the Hollywood treatment in David Fincher’s upcoming movie, The Social Network, based on Ben Mezrich’s book, The Accidental Billionaires, about the early days of Facebook.

Parker also served as an expert panelist at this year’s TechCrunch50 a few weeks ago.

Mr. Parker joins George Zachary, Keith Rabois, Adam Ross, Adam Pisoni, and David Sacks on Yammer’s board. The latter two serve as Yammer’s VP of Technology and CEO, respectively.