Recommend me some musical artists/songs

[Reef]

I registered at napster and got my free trial. So that means unlimited downloads for the next week. I've got the core of hip hop, R&B, some rock/alternative. Just today, I've downloaded close to 1000 songs but it feels like I'm only touching the tip of the iceberg.

Please recommend me some other musical artists/songs in these genres

what I currently have
As for rap: 50, 2pac, eminem, dre, snoop, ludacris, etc..

As for rock/alternative: Blink (old school), Hoobastank, Linkin Park, Goldfinger, pennywise, etc

other: R. Kelly, Sean Paul, Marley