Rather than donating money to charity chuggers, who pocket 50% of the monies for 'administrative' and tax purposes, do something better for a change by donating surplus computing power to research institute that can, in the long-run, benefit man-kind. And I know for a fact that everything I donated will be put to good use, unlike that of charities.
For the past month I have been donating computing power to the World Community Grid via United Devices client (you can also use the more popular BOINC client). Because the client only takes up idle CPU time (and it rarely put the processor under stress), electricity consumption is minimal. I only turn it on when I am actually using the computer, rather than leaving my PC on 24/7. Right now there are four projects on WCG, two of which my PCs are crunching for: FightAIDS@home and the Fiocruz Genome Comparison Project.
United Devices client calculating a WU for the Genome Comparison project on Windows XP
There are plenty of distributed computing projects around to suit anyone. CERN's LHC@home would probably suit physics geeks and Einstein worshippers more. Sci-fi nerds would most likely prefer to run SETI@home. Then there's the PS3 - Folding@home does demonstrate the crunching capability of STI's Cell processor.