I don't know if this subject has been posted before...what are some of your favorite cover songs.
Linda Ronstadt: Tumbling Dice
kd Lang: Halleluja
Rolling Stones: Just My Imagination
Beat Farmers: Powderfinger
Social Distortion: Ring of Fire
Robert Palmer: Bad Case of Loving You
Bangles: Hazy Shade of Winter
Beatles: You Really Got A Hold On Me
Fugees: Killing Me Softly
Fiona Apple: Across the Universe
Freedy Johnston: Love Grows (Where My Rosemary Goes)
Sly & Robbie, featuring Amblique: Walking on the Moon
..Of course, the list goes on forever

these spring to mind...

Joan Baez "Who Do You Think I Am?"
Joan Baez "No Mermaid"
Linda Ronstadt "Willin'"
Linda Ronstadt "Roll Um Easy"
Linda Ronstadt "Poor, Poor Pitiful Me"
Cowboy Junkies "To Lay Me Down"
Lyle Lovett "Friend of the Devil"
Wailin Jennys "Old Man"
Harry Nilsson "Living Without You"
Harry Nilsson "Can't Live (if Living is Without You)"

Beatle's 'Baby it's You' and 'Boys'
Richie Haven's 'Here comes the Sun'
Amboy Johnny & the Dukes 'Don't Walk Away Renee'
Hollies' 'Sandy'
speaking of Linda Ronstadt...'Blue Bayou'
and of course
the Sundays' 'Wild Horses'

Bright Eyes 'Crazy As a Loon' I'm not sure this song has ever been released as an actual musical track. I made an mp3 from a video for some AOL Sessions. This is a great cover as well as my favorite John Prine song.

Johnny Cash 'Hurt'

Bobby Bare Jr. doing anything by Shel Silverstein. He puts at least one Shel Silverstein song on every album. I guess my favorite would be 'Things I Didn't Say' which I believe was originally recorded by Dr. Hook.

Smashing Pumpkins 'Landslide'

The Grateful Dead's version of Me and Bobby McGee

Mentioning Grateful Dead reminded me of another one. I always liked Sublime's version of 'Scarlet Begonias'. I believe it was on 40 oz. to Freedom.
There's a lot of great covers out there that I like. I just can't think of them right now. I loved Jerry Lee Lewis's last album, Last Man Standing. An excellent covers album with duets on every song.