The electoral map
This is the site to watch tomorrow evening, as the election takes place. It will update regularly with a color-coded map of the states, based on the odds of that state going for Bush or Kerry as currently indicated by the Intrade market prices.
The white states are the ones we should be focused on. You can also view a distorted map based on electoral vote count for each state.

Comments
This is a site created by the creator of Minix (precursor to Linux) it uses bunch of math to tally up current poll results:
http://www.electoral-vote.com/
Yeah, everyone knows about that one, Adam. :)
But that just looks at one individual poll. It doesn't look at all the information simultaneously, weighing all the factors and determinign a probability. Plus, it's not real-time.