"Welcome to the NHK" has a lot of really good music. I love the opening song, "puzzle" from Round Table. Also, "Hayate Combat Butler" has some pretty catchy j-pop for opening and ending songs including songs from KOTOKO. Maaya Sakamoto has contrbuted some good songs for various anime including the opeing songs of "Escaflowne" and "Rahxephon" and one of the ending songs of "Wolf's Rain". I love her voice.

It depends what kind of music you want. There have been three anime soundtracks that I have fully enjoyed and purchased:

Revolutionary Girl Utena
X TV Series
.hack//sign

Thank you all; I will look at the selection.