We went to a festival in Brackley a few years ago, called Gatecrasher. Headlined by Chemical Brothers and Prodigy, with a host of many many other awesome DJ's, and one of our friends took us to one of the trance tents to check out this guy called Yoji. I'd never heard anything of him before, but for the 20 minutes of his set we saw.. I was just engrossed completely. Trance generally isn't my bag but this was awesome, the video below isn't as good a representation to when I saw him because the tent he was playing in was at least half the size of the one in this video:
YouTube - Yoji Biomehanika @ Sensation Black 2004 - Full Set 8/9
Also, at this years Glastonbury I wandered away from the Pyramid watching Stevie Wonder 'cause I needed to piss, and went to one of the other stages because it was so packed. Anyway I winded up watching the end of Orbital's set and they're arguably the best dance act I've ever seen live. I caught the song which they closed on which was Doctor? SO. GOOD. And some tool from Dr. Who came on during it but I had no idea who he was. This is the exact footage of the show I saw:
YouTube - Matt Smith & Oribital at Glastonbury 2010