Very Preliminary List of U.S. 2010 Congressional General Election Sites
Congressional Election Assessments:
Nate Silver's 538
Sabato's Crystal Ball
Charlie Cook's The Cook Political Report
The National Journal's Congressional Connection Poll (conducted with Pew Research Center)
Also see Charlie Cook's pieces in the National Journal every Tuesday and Friday
Major Newspapers' Congressional Election Sites:
New York Times' House Race Ratings
The Washington Post's Election 2010 Page
Collated/Aggregate U.S. Political Polling:
Pollster.com by Blumenthal and Franklin -- tracks national and state polls over time.
The PollingReport.com
Real Clear Politics (RCL) Polls' page
Poll Track (National Journal subscription required)
Just A Few Organiztions Polls' Pages (see lists of online poll sites below):
CBS Polls' Page and
The New York Times Polls' Page
ABC Polls' Page and
The Washington Post Polls' Page
NBC/The Wall Street Journal Polls' Page
The Los Angeles Times Polls' Page
Rasmussen Reports
Gallup's Election 2010 and
Politics and
Gallup blog on 2010 election Pages.
There are many, many extensive lists of online poll sites, such as:
CISER at Cornell University
Georgetown University's Library
The American Library Association (a bit outdated circa 2006)
The Miller Center at the University of Virginia
Aggregate Political Market Data:
Iowa Elections Futures Market
Paddy Power's U.S. Politics Page
Betfair (click "Sports" tab, then scroll down the "All Markets" column to "Politics").
Intrade (under "The Prediction Markets", click "Politics"). Intrade is owned by Tradesports.
See Jackman's Blog "election betting" list.