Fellow Vancouverite Tim Bray points to the Electoral Vote Predictor, but it predicts nothing, as it asks who would win "if the election were held today". Elections aren't held "today": they're held on the day they're scheduled, and they're always after polls are taken. So the EVP it's giving you a snapshot of now (or, more accurately, yesterday, since it takes time to take the poll and aggregate the numbers).
The Iowa Electronic Market President winner take all market [graph], on the other hand, is making a prediction: it asks traders to guess (and put their money where their mouth is) who will win the election when it's really held, in November. Not who will win today. (Oh, and the vote share market is interesting, but the point is academic: you don't become president by winning the popular vote. You become president by winning the electoral college.)
Marginal Revolution points to a Tradesports graph suggesting Bush is in trouble. But Sacha says, after the Democratic Convention, buy Bush.