A while back there was a project to do remixes of classic DooM tracks. It's titled The Dark Side of Phobos, and you can download all of the songs for free here
http://doom.ocremix.org/main.html
First off, it's easily some of the best music I've ever heard. Granted, the fact that I've literally been playing DooM almost all of my life (since I was five or so).
It's got a nice mix of metal, techno, and other various remixes. Check it out, it's worth the time.