Probably Cowboy Bebop, and Hack Sign. Gundam Seed has cool music too.
The Digimon Soundtrack (All the seasons, especially Tamers) is my favorite, followed by Hack://Sign and Rurouni Kenshin.
Azumanga Daohi, Nurse Witch Komugi, Magical Play, .Hack//Sign
Anything with Yoko Kanno, except Escaflowne (good, but not as good as the others).
I’m kinda particularly directed to the Hellsing: RAID Soundtrack…
Haven’t listened to Hellsing: RUINS enough to rate it at the same level…
I still believe that anything .hack related has good music.
I agree with you wholeheartedly.
.hack has great music, and every anime fan knows it.
I liked the music from the games too.
Eh, haven’t played any of the .hack games or heard any music from it, but I bet it’s good.
Another good anime soundtrack is Cowboy Bebop. The music is very good in that anime as well.
Key the Metal Idol. There are some absolutely stunning vocal songs there.
I like the music in Noir.
Walhalla respect++
Man, gotta love the Noir music.
Heat Guy J has some of the best tunes ever though 
Im quite partial to Last Exile too
Ah, yeah. that slipped my mind. I cant belive it. Yuji Kajiura is probably my favorite anime composer right now.
Naruto and SEED Destiny’s soundtracks are nice.