Will bitcoins do?
I'm set up now. If you send bitcoins to 1MtLKoe8H1mJraCy9jiZ2Cpd19Hqm1dy9U [EDIT: don't send money there; no one did at the time and I don't have the key anymore] I will send money to the AMF (that I wouldn't otherwise donate) at the current Mt. Gox exchange rate.
I'm willing to move up to $500 (25 BTC) this way.
Giving money to effective charities is one of the ways we can have the biggest positive impact in the world. If you've been thinking about giving to GiveWell's top-rated charity, the Against Malaria Foundation, but haven't gotten around to it, perhaps this will help: make a donation of up to $2K and I will match it 100%. I'll match up to $20K this way.
(Any money left over at the end of the year will also go to the AMF. That makes this a donor illusion, in that you're not actually affecting the amount I give them this year.)
I made the same offer on my blog