Charity Engine is half nerd feel-good project, half lottery–and as far as I can tell, completely great. The idea is simple (and perhaps familiar, if you’ve used similar distributed computing systems before, such as Folding-at-Home): When your computer is idle, Charity Engine uses its spare processing power to crunch numbers for scientific research projects. Together with thousands of other computers around the world, your Mac or PC is part of a giant, distributed supercomputer.

Since large-scale computing time isn’t cheap, research organizations or companies will pay for access to the virtual supercomputers. Charity Engine takes that money and sends it on to charity organizations like Oxfam or Doctors Without Borders. In short, you donate by paying your electricity bill. And if that weren’t enough, Charity Engine randomly selects a participant every so often and gives them a cash award.

If you’ve got a computer that has to be on all day anyway (and you or your employer doesn’t mind a slight increase in the power bill), it’s a dead-simple way to divert some of your money into charities in a very efficient way: Charity Engine estimates for every dollar of computing power you contribute, they are generating $10 to $20 worth of real money to be sent to charities.

(Which seems like a lot of money! So I suspect the organizations paying for the computing time are paying a premium over standard market supercomputing rental rates.)