The Bravery
OK Go
Green Day
Maroon 5
I'm sure there's more, but those are my top 4
Oh and bands/artists I have seen (although none of them were on my list): David Crowder Band, Flyleaf, Skillet, Sanctus Real, Family Force 5, Hawk Nelson, TobyMac, MercyMe, Chris Tomlin, Jeremy Camp, Natalie Grant, Group 1 Crew, Krystal Myers, BarlowGirl, Stellar Kart, and Francesca Battistelli. My youth group took us to lots of festival type things, I didn't go see all those individually. Ones in bold I thought were especially good.