Assuming they get back online within a day or two, tradesports.com is terrific.
The vig to bet on sporting events is a small fraction of going through an old fashioned bookie. Nice thick markets for politics & elections too, and they always come up with new, original stuff to bet on- like will Kobe get convicted, terror alert color code futures, and of course their claim to fame- the Saddam futures.
Good stuff...and based in Ireland, not some unstable third world country.