Best resource, in my opinion, is Five Thirty Eight. For the uninitiated, the guy who managed Baseball Prospectus analyzed all the polls, finding their biases, figuring out what indicators really matter and nailed it in the 08 election. Now his blog is hosted by the NYT: http://fivethirtyeight.blogs.nytimes.com/
Anyway, he has Obama in a solid lead right now due to him having a slight lead pre-convention, Romney getting almost no boost in the poll from the RNC (which normally would be expected to be higher) and Obama getting a decent boost from the DNC. Has Obama at 78% odds (92% if election were held today).
Lack of a bounce from the RNC seems to indicate this isn't an election Romney can win. Certainly one Obama could lose with a big enough sudden downturn in the economy, but nothing the Romney campaign does at this point will overturn the fact that swing voters just don't really like him and, sluggish economy aside, seem to want to give Obama the benefit of the doubt.