I love the concept behind Audio Autocracy - craft a mixtape for every year that you've been alive using music from that time period. It would serve an educational purpose for yourself and it would create a time capsule (albeit broad) of the time that you've been alive. It would also be interesting to note the differences between my selections from a particular year and a friends - letting our own personalities spill into the song choices. Long story short, go check out (and keep up with) the mixes at Audio Autocracy.