ACIDplanet is a community site mostly geared at users of Sony Acid software. There are regular remix contests and users can upload their own original work as well. Looks like a technically accomplished and well featured site.
I don’t find the licensing terms very attractive though. I’m not a lawyer, but here is how I understand some of the relevant parts of the terms and conditions:
All contest entries become the property of the site owners (Sony Creative Software) – including their ability to re-publish the remix in any medium they please without compensation of the remixer. The remixer doesn’t get to do anything else with their contest submission, not even post it for free somewhere.
Uploading original material gives the site owners a permanent license to republish that uploaded material in many ways including as an included free item in an otherwise commercial offering. It would appear that they could very well release a CD with one piece of crappy software and 20 fantastic tunes from the uploads to acidplanet.com, charge 20 dollars for the software and include the songs for free. So people might actually buy the CD just for the music and the original creator would never see a penny.
I generally won’t cover remix contests on sites with such one sided licensing terms.