Former congressman Rob Simmons, but I was only 6-7 years old and don't really remember it too well.
As for musicians, none of them are really famous as in household name famous, but they're all relatively well-known: Peter Hammill (along with High Banton and Guy Evans, but Hammill is the most famous), Steven Wilson, Annie Haslam & Michael Dunford, Daniel Gildenlow, Roine Stolt (and the rest of TFK, sans the drummer), all the members of Riverside, Mike Keneally, and Vincent Cavanagh.
Edit: Also, a relatively famous actor goes to my college. I think I've talked to him once or twice but I didn't know who he was at the time.