The Blue Planet Run Foundation is running a pretty cool event this October: you can sign up to join Team Blue (it costs US$30, through donation or pledges) and run, walk or cycle "30 miles in 30 days," from October 1 to 31. (Isn’t that 31 days? I guess you get to have a day off.)
Proceeds go toward bringing safe water to children in Tanzania, and if you don’t want to participate but would like to contribute, you can still donate to the project without getting off your couch. (Donate to me, if you want—I promise I’ll do the 30 miles.) Oh, and I looked it up—we’re looking at 48.3 km, metric folks. Sign me up—I need a goal for October.