Darren Oliver

50+ Games, 2.90 ERA or lower, 2009-2011
Mariano Rivera
Darren Oliver
Heath Bell

It is still relatively early, but it looks like Darren Oliver might be the only one to do this again in 2012 (Rivera is hurt and Heath Bell has an ERA of 6.65).  He's 41 years old, with his 9th different team (including 3 different stints with the Rangers).  He might have been better off being a reliever his entire career (his career ERA would probably be a lot lower than 4.58). 

Oliver has pitched in 21 games (18.2 IP) this year and has an ERA of 1.93.  He still doesn't have a World Series ring (he came really close last with the Rangers in his first trip), so he might not be finished for a while.