Well I think it's about time there was a thread for this! So there's these musicians who call themselves The Vulcan Freedom Fighters and basically what they've done is taken dialogue and stuff from various TOS episodes and mixed it with some of their own music. It's pretty cool stuff IMO, this is their website:
http://www.vulcansrock.com/

And all their music is free, you can download their songs from their site:
http://www.vulcansrock.com/freemusic.html

They have also made a few videos with their songs, you can watch some of them by visiting their YouTube page:
http://www.youtube.com/user/sporktube

So far my favorite songs are "Romulan Divide" "Khan" and "Klingon Advance"

I'm sorry, is this getting a little too nerdy?