I'm currently GMing a campaign over the net (2 full sessions and one semi-personal so far), and I'm using soundtracks even more than before. I'm trying to come up with 3+ tracks per major location and per major NPC.
It seems a convenient thing to use a service allowing one to share and play lists of tracks online, thus making it a matter of dropping a link into the chat window (and also allowing for simultaneously playing different tracks for different players).
Speaking of which, at first I thought the only way to do it is to make a closed server with some sort of repository, but apparently
there are such 'open' services that are legal according to the DMCA. The ability to quickly find a track by name (in case of some improvisation) and instantly offer it to the players is neat.
Regarding the tracks themselves, PC game soundtracks seem to be quite spot-on quite commonly. For instance, tracks out of Tiberian Sun: Firestorm, Deus Ex, Mirror's Edge, Mass Effect 2, Orange Box/Portal, Star Control 2.
(Originally wanted to start a new thread, but there's no point if there's one perfectly matching the topic.)