One reason votepair.org hasn't paired many voters
You may have heard of the vote-trading concept, where a voter in a "decided" state (whose vote will make no difference) who wishes to vote for a major candidate pairs up with a voter in a swing state who wants to vote for a minor candidate. The idea is they swap choices. The swing state minor party supporter votes for the major party candidate (typically Kerry this time) and has a chance at making a difference in the swing state. The decided state voter, facing a large likely margin in their own state, votes for the minor candidate, boosting the national popular vote total for that candidate, which is all minor party voters care about since they don't plan to win.
Sounds good, but as you will see at votepair.org, they have 19,700 waiting and only 2300 pairs matched up, so the vast bulk of eager Kerry supporters won't get to swap.
There are many reasons to explain this. Some are simple. There are many more Kerry supporters than minor party voters. There are many more people in decided states than in swing states. And of course some people may wonder how much to trust the honour system used in vote swapping. You are supposed to meet your counterpart, and judge that they aren't a republican trying to play tricks, though in theory there is not much for them to gain by doing so.
One problem is the trade offers a lot to the Kerry supporter -- trading away a meaningless vote that can't change the results for a precious vote in a swing state -- but offers effectively nothing to the minority voter, since it doesn't affect the vote total for the minority party. (Indeed, it may hurt the minority party's prospects in that state.) As such, you are only going to get people who were more than happy to vote Kerry anyway, as they now will feel they gained from the trade.
Of course, a real market in votes is illegal, as these orgs know, but you can't ignore the realities of what makes a market work.
As such, the sites should consider offering a larger trade. They should let minority voters set a price for their switch, which could be 1.5, 2 or even 3 minority votes in the decided states. Then both sides would gain and it could up the count. (Libertarians, who value deeply the concept of win-win contracts as a basis of society, would be particularly swayed by this, and they are one of the largest minority parties.)
The existing 2300 might still be willing to do it for just one vote (remember, they probably were considering doing it for nothing.) Others could ask higher and higher "prices." Of course ask too high and you won't get anything, the voters will be allocated first to those asking less.
Yes, you can do a 1 for 1.5 swap, and I think that's the easiest and fairest. In this case each minority supporter is given two people to arrange swap with, one fully, and the other 50%, in that this other is expected to have an identical 50% deal with another supporter of the same minority candidate.
(Ethically, after you arrange things with the first voter in a 50% partnership, you would need to tell them if the 2nd voter fell through, and get it resassigned. Ditto for a 2 for 1 exchange.)