Also a persistent arb between Intrade and Betfair. Same direction -- Intrade Obama underpriced. The Obama underpricing may be the work of a single pro-McCain trader, who looks to have dropped about $200k so far supporting his guy.
I was just thinking of this today before I saw this - some people must be making big money arbing between Intrade, those Iowa University markets, Betfair, and the others.