The Canadian Broadcasting Corporation is letting the public
remix Wagner's Ride of the Valkyries.
Remixes have to be a maximum of 2 1/2 minutes long, may be in any style (such as "classical, dj, world, mash up"), and are due in on the 21st of August. This contest is open to Canadian residents only, though there doesn't seem to be anything prohibiting non-Canadians from downloading the original audio file, remixing it and not entering the contest.