If you use a MSFT-based messenger, and are willing to update to Windows Live Messenger 8.1 (the latest/greatest? version), keep reading.
Microsoft has launched a new charity campaign called "i'm", where they will donate money to a charity of your choice, for each IM you send.
For the official site, head here:
http://im.live.com/Messenger/IM/Home/
For the inside/easier-to-understand scoop from a MSFT program manager on the Windows Live team: http://messengersays.spaces.live.com...9E!25315.entry
As a former 'softie, I can tell you that the company's commitment to giving back is huge -- it's nice to see that they're finding ways to get the general public involved as well.