I could throw my whole iTunes collection in here, but you'd need 21 days to listen to it all. Even posting it all would take too much time and posts.The Wiki needs a hand, and Bwian's will gladly take the rest of your (carcinogenic) body!
The Answer to the Great Question of Life, the Universe and Everything is...
Depends on the mood I'm in, but sometimes I just stick to the RuneScape music (so much of it is just so great and still makes me so nostalgic) but if I'm doing a longer session, I prefer to switch it up a bit and throw on some more ambient-leaning electronic/instrumental music like:
Boards of Canada Four Tet Burial Stars of the Lid
Helps keep you in the zone, and isn't too distracting!