My buddy Scott Hanselman and his coworker (and often destination of referrals on my blog) Greg Hughes have a great idea: donate all of one's Google AdSense revenue to the relief efforts in South Asia.
I would say that one doesn't need to restrict one's self to just AdSense, but that is a great starting point. Further, Greg and Scott are beginning a campaign to encourage Google to help automate the process for users of AdSense.
Do the world a favor: Participate, Donate, and Contact Google along with all of us. It's worth it!
Update: Stuart Celarier has a great list of other agencies that one may consider, too: