edit: this site is awesome here are some my favorite essential mixes you may have missed
mr scruff http://mxtr.fm/KBmUTW
Essential Mix with Audio Bullys http://mxtr.fm/IDmIIU
the goa mix ( http://en.wikipedia.org/wiki/Goa_Mix ) http://mxtr.fm/K4Yian
some other good sites to download dj mixes are http://www.livesets.us/ and http://themixingbowl.org/ both great.