this turns out to be a very nice thread!
here are some links i found useful:
http://www.vgmusic.com/
(video game midi music)
http://www.mirsoft.info/gmb/index.php
(game music base)
http://www.rpgamers.net/Games/Music.cfm
(collection of mirror sites containing game music)
http://gamemusic.emugaming.com/
(more game music in various formats)
http://www.arkasizer.com/rabite/sound/
(even more game music)
if we should collect more useful links here, i will pin this thread as it could
be valuable addition to the game music which is listed on abandonia's
main page...