VotePair

Vote pairing - vote trading - whatever you want to call it - is a way for Nader-type voters to cast their vote for their favorite candidate without 'spoiling' the election. The VotePair website matches Democrats in 'safe states' with Nader voters in 'swing states' and essentially has them agree to trade votes. Nader gets his vote - just in a different state, and Kerry gets his vote - only, in a state where that vote will actually matter in deciding whether he becomes president or not.

VotePair.or explains it in their FAQ like this:

Through Vote Pairing, Green Party members, Independents, Libertarians and others sympathetic to the David Cobb, Ralph Nader and Michael Badnarik candidacies in swing states register their personal decision to vote for Kerry-Edwards while Democrats in safe states register their personal decision to vote for Cobb, Nader or Badnarik. After a participant enters his or her home state and candidate preferences, he or she will then be "paired" with another progressive voter to give everyone a vivid personal glimpse of how this big political coalition is actually working. Votepair.org allows paired partners to contact one another directly (by email or other means of communication) to engage in a more detailed political dialogue. This can also provide an opportunity for participants to feel comfortable that others have joined the alliance in good faith. We do NOT facilitate any means of communication other than email.

The higher-level purpose of VotePair is to compensate for the shortcomings of the electoral college.

I'm signed up - just waiting for my marching orders. Just figured out I need to cast an absentee or early ballot, though - so not sure how it'll work out.