Opensecrets.org

http://www.opensecrets.org
Find out who made contributions to whom in the 2008 Presidential Donations. OpenSecrets.com list contributions by State and even Metro Area's, along with loads more election statistics and information.

Vote Smart.org

http://www.vote-smart.org
Project Vote Smart (PVS) provides a comprehensive database about thousands of candidates and elected officials for President, Congress, Governors and State Legislators.

RocktheVote.com

Rock the Vote is a non-profit, non-partisan organization, founded in 1990 in response to a wave of attacks on freedom of speech and artistic expression. Rock the Vote has also launched a 50-city bus tour, culminating its journey on Election Day, November 2nd. Taking its message of youth voter registration to dozens of the most hotly contested markets this election year - via musical concerts, college campuses and major political conventions.

FactCheck.org

This is a nonpartisan, nonprofit, "consumer advocate" for voters that aims to reduce the level of deception and confusion in U.S. politics. Their site monitor's the factual accuracy of what is said by major U.S. political players in the form of TV ads, debates, speeches, interviews, and news releases. They seem to apply the best practices of both journalism and scholarship, and to increase public knowledge and understanding.