Cool mostly from a 'because you can' perspective, UCSC Human Genome Browser. Download your own source code :) Someone needs to invent a BCEL-like API for parsing this stuff. Though, I guess if we've scrapped the idea that God wrote the code 4000 years ago and compiled it to DNA, then we're left with the idea that (God) evolved it, and we should be looking for ecologies of 'selfish genes'. And since ecologists have such trouble working out relations beween highly observable animals, in real-time, what chance is there of doing it for a static snapshot of billions of base-pair sequences?
Time to get into bioinformatics.. don't want to be writing websites for the next 50 years :)