This page, like this one made by Randall Munroe of xkcd fame, which inspired it, is following the 2008 U.S. Presidential election based on data from Intrade.com's state-by-state prediction markets.

The map is shaded according to the states' probability of going for Obama (blue) or McCain (red). As the Intrade markets converge toward their final values the map should likewise converge to each state being either bright blue or bright red.

The "Call state at" slider controls when a state's electoral votes are assigned to a candidate. At 50% votes are assigned to whoever is more likely to win the state. At 100% it requires the Intrade market to have collapsed to certainty before they will be assigned.

The "Paranoia" slider tilts the results to account for any factors you think the Intrade traders have overlooked – Bradley Effect, Reverse Bradley Effect, vote stealing, unpolled cell-phone-only young voters, etc. Since I'm a Democrat, positive paranoia values increase McCain's chance of winning. When the slider is selected, hitting '0' will set the value back to 0.

This page suffers from the same two weaknesses as the xkcd page: it assumes states' individual probabilities are independent and ignores the potential splitting of the electoral vote in Nebraska and Maine. If you need greater statistical rigor, check out FiveThirtyEight.com.