Beat the Clock by bassling
Ableton Live is my choice of digital audio workstation and they recently held a remix competition.
They offered sounds from a few artists and there was a clever rule that you only had 24 hours. My entry is above, it took less than ten hours.
It was a great move by Ableton, who also offered the Lite version of Live, in partnership with Soundcloud, who host music online. I think it's fostered a sense of community because you naturally seek out other remixers to hear how they approached the material.
Below are a couple of remixes I've enjoyed:
Philipp Mann - Beat The Clock by Philipp Mann
KlanKman - 24h beating by KlankMan (Fuzzy Wuzzy)