I was recently in The Garden of Unearthly Delights, a wonderful area set up in the parklands of Adelaide for the fantastical Fringe Festival.
Within the space of commercial and creative activities and individuals, was a wonderful open dancefloor, Silent Disco.
It is a couple of DJs from Netherlands, who thought up this idea when they were DJing at an event where they were 'complained apon' due to noise levels.
Silent Disco gives you headsets and you dance to your hearts content, choosing the music of either of the 2 dj's playing. Its wonderful to watch people dancing about (so entertaining!!) while still carrying out a conversation - and all under the milky way! (or wherever you choose actually).
If you are having a festival - anywhere - consider this!

http://www.silentdisco.com/frameset.php?taal=2
http://www.gardenofunearthlydelights.com.au/