If there is ANY question about you being challenged at the polling place, or if you are a victim of fraud OR suspect fraud going on, immediately call the Election Protection hotline at 1-866-OUR-VOTE (1-866-687-8683 which is toll free). Also, visit http://www.ourvote.com
Additionally, People for the American Way have put forth a group called “Election Protection” at http://www.electionprotection2004.org/index.html — it’s a clearinghouse of information about voter rights.