“This site lets you browse every vote in the U.S. Congress since 1991.”
Some of the categories by which the results can be broken down include: chamber, year, state, member, party, attendance, margin, and vote type (i.e. nominations, treaties, key votes, VP tiebreakers, etc).
The site also provides RSS feeds of new votes, which can be viewed as a whole or individually by member of Congress.
A pretty impressive service of WashingtonPost.com