(On Dee3s advice ...)
There are a fair few good net-labels out there offering free music, that is also of a high quality.
As well as www.thinner.cc and www.audioaubergine.com (as both mentioned in the 'mixes to download...' thread), there are others and also labels that offer their previously released work for free.
One of the best netlabels IMO is www.micromusic.net (offering video game style bleepy-electro stuff), which although you have to be a member (free of course) to join, offers so many excellent tracks (including that by the likes of Cylob) that I would most certainly recommend a look.
One of my other personal favourites is:
People like Andrew Weatherall and Luke Vibert have championed that stuff, not loads there but some very interesting music. Also, try:
Although a lot of it is completely impenetrable noise music, there is some good IDM (look for the 'Up-Link Data Transmissions' mini-album) and Euro-style New Beat that will appeal to the acid-heads here.
That should keep some of you busy!!