Most people who were a part of the scene in 2000 remember The Product (1). I remember it winning The Party and being struck by how impressive their work was. If you're on windows, I guess you can download the demo itself (2). At 64kb, it should be a pretty quick download ;-) Their impressiveness has only gone up since 2000, as you can see by watching Debris (3), which at 177kb beats the living crap out of most things…
I imagined that demo skills would eventually die and the more recent stuff would just end up being bloated or lame. But it really has improved. Infeasibly improved. Debris is amazing. But it isn't the only more recent amazing demo. Someone once asked me whether there was a limit to how realistic demos can be made. I would normally prate on about Shannon information or something, but it was a very smart mathematician…
I don't think he published the code, because it was written for Renderman shaders at ILM, though.
His blog is a must read if you're mathematically inclined.