I came across the site of charitywater, who put an enormous effort into their website to help and drill wells. If it’s your birthday, you can sign up there and let people give money to those guys.
As a hydrogeologist, I want to point you also to hydrogeologists without border, who work along similar lines, but are trained hydrogeologists. I guess already from their name and the similarity to the probably better known medicines sans frontiers / doctors without borders, you can easily derive what their goal is.
Update Wednesday; April 22, 2009: Drinking Water for Life is another option if you are looking into ways to support people who can’t afford drinking water.
Update Sunday; April 26, 2009: Please check also “charity:water” out