I think I posted this site already, long ago but it's certainly worth repeating and now that I think of it, worth putting up on my permanent links collection as well, which is an oversight I'll be sure to correct a.s.a.p. Digitalcharity.com is an easy way for you to give a little, with a bare minimum of fuss. It's a selection of sites that - with help from sponsor programs - will allow you to contribute to various charities simply and easily. Just pick a charity, click a link and you're done. In fact, I'd say it takes a total of 2 minutes (if that) to click through all the ones listed at the top of The Hunger Site page and they're all worthwhile causes. I particularly like the Animal Rescue Site - each time you click, sponsors pay for a bowl of food for a homeles, sheltered animal - but I'm making it a point to go there each day and click all of them since it's so easy, like I said, there's really no reason not to.
A more extensive list of charities like this can be found here on this page, which a poster on Fark owns and offered up in one of the forum threads regarding makethatdifference.com, yet another charitable meta-site.