Brad Reed has compiled the extensive list, but I'll give you the Reader's Digest version here. Go read the full article at Alternet:

10: Bush Gets Re-elected
9: Alberto Gonzales' Congressional Testimony
8: North Korea Conducts a Nuclear Test
7: Colin Powell's Bogus WMD Presentation at the U.N.
6: The Terri Schiavo Affair
5: Bush and Condi's Excellent Gaza Adventure
4: "Brownie, You're Doing a Heckuva Job"
3: Abu Ghraib
2: 9/11
1: "Mission Accomplished"

Seems like the hardest part is simply narrowing it down to just 10.