MTV
Exactly what you've always wanted out of a MTV website but never got until now: MTVmusic.com. Huge archive of videos, organized by artist (e.g., David Bowie, Elvis Costello, Prince, Madonna, Talking Heads) with an interface that resembles Hulu. This should have existed years ago. Update: MTV Networks also launched an API. (Is someone finally reading my "If I Ran MTV" rants from 2004?)