Well-known overclocker/reviewer Shamino takes a set of 2x512MB GSKILL PC8000 for a test-ride. He pumps up to 3.2v through the poor things without killing them. Although only a 1GB kit, this is some fast RAM. 8O
http://sg.vr-zone.com/?i=4123
522MHz at 3.2v isn't very stable, but I found stability at 515MHz, CL3-3-3-5 with 3.1v.
http://sg.vr-zone.com/?i=4123