The idea of a mashup is simple and mixing a few songs together seems easy, but it’s very difficult to do well. One of the best collections that I’ve heard in a long time is Sounds for the Space-Set from the RIAA (Robotic Intergalactic Astro-Artists). It combines bit from sci-fi films and mashes together older and newer music to create something that is a lot more than the sum of the parts. A great sense of humour runs throughout the tracks an infectious beat and diverse sources that are sometimes hard to identify. Fun and free!