Hmm, some of my favorites:
Wolf's Rain has a great soundtrack all around (and it happens to be one of my favorite animes).
RahXephon has some great music (part of the point of the show), though I can't seem to find any of the really good stuff on YouTube
Lastly no anime music thread would be complete without Cowboy Bebop.
So I'll share something from another of my favorite anime soundtracks.
Ghost in the Shell: Stand Alone Complex it's just an awesome anime, and the soundtrack completely rocks. Of course we have Yoko Kanno to that for this one as well.
Inner Universe - opening song
And Lithium Flower -ending theme.