Besides
The Hunger Site, now
Ripple.org is also on Wikipedia, with sources. At both sites, you can click to donate to various causes at no cost to you, and you can also search to donate on Ripple. They have banners you can post on your profile or elsewhere.
I can't check them all, but there are links to many more click- and search-to-donate sites
here and
here, plus you can apparently click at
Feed SA and search at
Oblatoo,
MagicTaxi and
Everyclick.
BTW,
Giving What We Can will start to provide resources on making a difference in a few months.