Interesting! I've never seen a charity asking for your mouseclick instead of your money. But Aquaplastics 2005 (via gebsn) seems to do just that. If they reach 1.5 mio clicks on their website by June 22nd, then the European plastic industry will donate EUR 150'000 (10 Cents per click) to WaterAid to provide people in Ethiopia with clean, safe water & sanitation. Hell, I've clicked on infinitely sillier links than that - and so have you!
FYI: the counter currently stands at only 324'140 clicks ... 1'175'860 more to go!