The site's founder is Nate Silver of Baseball Prospectus, a website dedicated to an absolutely staggering study of baseball statistics. Silver's brought his incredible statistical knowledge into politics on FiveThirtyEight, using a combination of demographic studies in each state and weighted averages of national polls to create what he claims is a considerably more accurate portrayal of what the presidential race looks like than what any single poll can give. Here's a recent profile on Silver done by New York magazine. This guy's real good.
The blog includes daily updates on polls, as well as some dispatches from swing states, and state-by-state breakdowns of political trends. They haven't gotten to Vermont yet, though, so bookmark it now. Actually, bookmark it anyway — it's possibly the most interesting and intelligent source of information I've found on the election yet.
And by the way, Silver is currently predicting Barack Obama to get about 344 electoral votes, and John McCain to get about 194.