Girl Talk - Night Ripper.
Not as old as the others - this came out in 2006 I think. I remember reading about this album and the review really piqued my interest.
So, imagine someone throwing most of your music collection into a blender. This is kinda the result. Has been described as "a lawsuit waiting to happen" Girl Talk uses creative commons licences to appropriate loads of segments of tunes, and recycles them into new creations.
So it isn't just "mash up", and it isn't djing either.
It's fun to play spot the tunes you recognise, and there's a lot in there. I think I haven't listened to it in so long because his subsequent albums (Feed The Animals, and All Day) were also so freaking awesome they took over.
Great stuff.