Male
1. YouTube
2. Facebook
3. Google
4. Yahoo!
5. ESPN
6. AddictingGames
7. MySpace
8. MiniClip
9. IGN
10. NFL

Female
1. Facebook
2. Google
3. YouTube
4. MySpace
5. Yahoo!
6. AOL
7. PerezHilton.com
8. MSN
9. Amazon
10. TMZ

Source: eMarketer
http://www.emarketer.com/Article.aspx?id=1006736