Tori Amos has done a lot of awesome covers. One of the main attractions of seeing her live.
A Case of You (Joni Mitchell)
Famous Blue Raincoat (Cohen)
Love Song (Cure)
Smells Like Teen Spirit (Nirvana)
'97 Bonnie & Clyde (Eminem)
Also you all my find this site sort of "neat"
http://www.cover-vs-original.com/