I am in love with this site.

It's called Cassette From My Ex, which wouldn't be a terrible name for a band, either.  All these different people contribute (some pretty well-known essayists, one of the backing vocalists from the Magnetic Fields) a couple paragraphs about mixtapes they've been given, explaining context and talking about the stories behind the songs on them, with the playlists included at the end.  Highly recommended.