Marc Andreessen proved back in the mid-1990s that he had technical chops as co-creator of the first consumer web browser, Mosaic. Then he learned how to lead companies through ups and downs at Netscape, Opsware and Ning. Now he is trying to out-venture the VC establishment as cofounder of Andreessen Horowitz, an investment firm modeled after Hollywood's Creative Artist Agency back in its 1990s heyday. He made seed investments in Twitter and LinkedIn, and bought into later-stage investments in Skype as well as 2011 IPOs Groupon and Zynga. Andreessen's street cred with entrepreneurs serves him well. Mark Zuckerberg asked him to join Facebook's board. Other investments include Airbnb, Fusion-io, Glam and Instagram. Andreessen also serves on the boards of Bump, eBay, Kno, Rockmelt, Stanford Hospital, TinyCo and Hewlett-Packard. Andreessen is nothing if not focused--he describes his travel routine: "I try my damnedest to never leave the 20 mile radius around my office."