See intrade for folks betting money on the outcome.
And after the election, for analysis of what it means in Congress, see TheCapitol.Net’s Capitol Hill Workshop: 2008 Election.

More

• Campaign Finance Information Center – from Investigative Reporters and Editors and the National Institute for Computer-Assisted Reporting.
• Campaigns & Elections magazine
• opensecrets.org – show me the money
• CQ Money Line – show me the money
• Iowa Electronic Markets – includes a political section – “real-money futures markets in which contract payoffs depend on economic and political events such as elections. These markets are operated by faculty at the University of Iowa Tippie College of Business”
• Politics1
• PollingReport.com