GoodSearch.com is a search engine that donates half its revenue, about a penny per search, to the charities its users designate. You use it just as you would any search engine, and it's powered by Yahoo!, so you get great search results.
Just go to www.goodsearch.com and set up your own charity.
Only 500 people searching four times a day will raise about $7300 in a year with no cost to them just great searches.