http://www.aubreyhodges.com, creator of the soundtracks for the Nintendo 64 ports of Quake and Quake II, has recently released both of them on his website. All tracks including some bonus songs can be listened to online or purchased for $10 in various audio formats.
http://aubreyhodges.bandcamp.com/album/quake-nintendo-64-official-soundtrack
http://aubreyhodges.bandcamp.com/album/quake-2-nintendo-64-official-soundtrack
There are several more soundtracks available on the site, such as Doom 64 and Playstation.