Thomas Lookup
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Congress.Org lists how Cong. Baker voted on key issues.
The Office of the House Clerk lists all official roll call votes from the U.S. House of Representatives.
An Explanation of Roll Call Votes is published by the Library of Congress.
C-Span Congressional Votes Library allows you to search for votes by subject and date.
VoteSmart lists major votes and how all Members of Congress voted on them.