Y Combinator's First Batch: Where Are They Now?
thenextweb.com
thenextweb.com
Another note: the beauty of YC isn't that Paul & co. pick home runs every time -- they don't -- it's that they pick teams that eventually hit home runs. Justin.tv is doing okay, but YC's investment in Justin in 2005 has netted it Socialcam (acquired for $60M) and Exec. YC's investment in Reddit also netted them Hipmunk.
And I'm only scratching the surface here -- YC founders always recruit great people into the YC program.