well this should be down your alley. basically a simple make your own mix tape site with thousands of 12 track mp3 mix "tapes"
confusingly called er. http://www.muxtape.com/

here's a sad one
http://mattpayton.muxtape.com/

here's a happy one
http://noah.muxtape.com/

but there's thousands. hours and hours of browsing.