Jimbo told me about IEM when I met him in Linz. A paper (PDF) describes the past elections and how the markets have been amazingly good at predicting their outcomes. IEM has a current market quote which is updated every 15 minutes. As of this posting, it is 40.6%/59.4% Kerry/Bush.
On IRC, crw, just pointed out a blog post on The SaltwaterPizza that used Google to see how many people said they were voting for one candidate or the other. The sample size was 104,789. This gave 46.8%/53.2% Kerry/Bush.
The results are disappointing for those of us who are hoping Kerry will win, but these alternatives to traditional polls are very interesting none the less.