MVR 3D have some incredible screensavers for download.

Naturally, the Matrix Reloaded screensaver is the one which jumps out at you, but on balance, I think that I prefer the other three. Whack on a Jimmy Giuffre MP3 or two on at the same time, and this is just about as mellow as you can get without chemical assistance.

Beware, though - you'll need a monster PC to run this lot. I've got one. ;-)