FreeRice is fun, but impractical (other than expanding your vocabulary).
Reusable canvas grocery bags are fantastic, but I forget to bring them with me to the store (I'm trying to remind myself more, especially now that I have a really cool looking one from Publix).
But now, all you have to do is search the internet and save the world!
Hoongle is a search engine powered by Google. Every time you search a term, they donate 20 grains of rice to the UN food program. Now, 20 grains of rice doesn't seem like much to me, but I guess it adds up. Every little bit counts, right?
Now let's see if I can remember to use it...