Here's a short list I compiled from some folks I've talked to.
The Art of the Start by Guy Kawasaki
Founders at Work by Jessica Livingston
The Four Steps to the Epiphany by Steve Blank
Getting Real by the guys from 37 signals (agile development for the non-technical)
The Lean Startup by Eric Ries (ok, it won't be published until Sept 2011)
I'm I missing any good ones?