On my music player, I have 614 artists. Some of these are single songs from samplers/soundtracks, but I'd say I have about 400 artists on my Zune with at least a full album from them.
07/22 - Melt-Banana
07/26 - Forever Came Calling & Primitive Man
07/30 - Warped (?)
08/05 - Knockout Kid
08/07 - Fireworks (?)