Lately, I've discovered mashups — for the uninitiated, it's digitally combining two (or more) songs into a (hopefully) pleasing new composition, an unintended duet. It's the musical equivalent of taking two completely different works of art and blending elements of one into another using PhotoShop; imagine inserting Marilyn Monroe into a Boticelli painting, for instance. Usually they juxtapose a currrently popular artist with a classic song from the 70s or 80s.
You can find mashup mp3 files all over the web; some of the ones that I like the most come from Go Home Productions. It helps when I actually know one or all of the songs involved, so mixing two songs on today's pop charts doesn't do much for me. A particular favorite is GHP's Rapture Riders, mixing Blondie's "Rapture" with the Doors' "Riders On The Storm."
Any favorites you'd like to recommend, in the comments?