All of the Ghost in the shell music is great, its very varried, and good for various situations in SR; Jpop for that japanese place downtown, classical stuff for that fine restoraunt, rock stuff (without singing) for those combat scenes, dance/tekno for the nighclubs, even some silly music for those times.
Mind you, i have not put this collection to use yet (we are starting up this Friday though) i also have:
music from the matrix (some cant be used, cause its too known)
music from blade runner (for when you want something that stays in the background more)
music from various CnC games (its made to be background music, and its great for tense situations between combat)
the music from mirrors edge (it does not fit the general grittiness that well, but its good for other situations with a different mood I think
I also use the following artist:
Apex Twin
Misen
Earthbound
I had to steer clear of my favourite music such as Muse or Daft Punk, cause that would get me out of the SR mood i think (not to mention that I would play it way too much

)
EDIT: Oh, i forgot to mention the fallout games, music frmo the old ones are great background music, and from fallout 3 you get the old music that might work in the barrens or something, I'm not sure yet.