One is the loneliest number
Stealing an idea from Mark, I have listed 20 artists who have exactly one song on my iTunes playlist. Your job is to identify that song. I have tried my best to avoid the one-hit wonder types, as well as bands of which I actually own CDs but only transferred one song to the list. I'll update as people answer them correctly.

1. 311 -- "Love Song" (Joe) -- You may be picking up on a theme ...
2. Beautiful South
3. Boyz II Men -- "Motownphilly" (Contrary SOB)
4. Cheap Trick -- "I Want You To Want Me" (Flax)
5. The Cult -- "She Sells Sanctuary" (Greg) -- Got it off the As Seen on TV compilation of songs from commercials.
6. David Alan Coe -- "You Never Even Called Me By My Name" (Joe) -- As heard during Brian's wedding
7. Fiona Apple -- "Across the Universe" (Victoria) -- Not sure why I don't have anything else by her.
8. Godsmack
9. Heart -- "Magic Man" (Contrary SOB)
10. Jesus and Mary Chain -- "Just Like Honey" (Greg) -- As featured during the closing credits of Lost in Translation
11. Lenny Kravitz -- "Are You Going to Go My Way?" (Tyler) -- I like this song. Don't really like anything else by him.
12. Mandy Moore -- "Senses Working Overtime" (Tyler) -- I'll count it, even though he guessed a bunch of songs off Coverage at the same time.
13. Mariah Carey -- "Vision of Love" (Sean)
14. Nazareth -- "Hair of the Dog" (Contrary SOB) -- More cowbell!!
15. P.J. Harvey
16. Prodigy -- "Breathe" (Joe)
17. Roxette -- "Joyride" (Contrary SOB) -- I think I have way too much Swedish pop in the collection
18. Son Volt
19. The Vines -- "Ms. Jackson" (Joe) -- Yup, it's that one. No one ever said I had a ton of musical taste, as seen by the list of artists on here.
20. The Zombies --"Time of the Season" (Sean)