This one's been out for awhile, but I don't recall posting it here. The Washington Post has put together a browsable and searchable database of Congressional votes that includes every vote since 1991.
You can even set up RSS feeds for timely updates.
Hmm... if you tied the RSS feed to a text messaging service, you could follow your representative or senator down to the minute. I imagine with a bit of creativity, you could even hardwire email responses based on the vote.