Last.FM is the best site for this.
Mine;
1. Sam Sparro - 600 plays (29 songs).
2. Christina Aguilera - 524 plays (189 songs).
3. Lady GaGa - 311 plays (53 songs).
4. Patrick Wolf - 231 plays (75 songs).
5. Green Day - 222 plays (140 songs).
6. Adam Lambert - 208 plays (26 songs).
7. The Saturdays - 172 plays (18 songs).
8. The Pussycat Dolls - 118 plays. (42 songs).
9. Ashlee Simpson - 117 plays (44 songs).
10. Porcelain And The Tramps - 106 plays (12 songs).