I have put a short list of ministries at the top of my sidebar. The reason they're at the top (except for the Aristotle quote which explains what my blog's title means) is because they're more important than anything else. I won't be adding more ministries to this list, for the simple reason that there would be no justifiable stopping point. There are simply too many worthy ministries, and I would always be guilty of excluding very deserving ones. So I just put a few that I know and are encouraged by.
The first is International Justice Mission. I love these guys. They go to countries where child prostitution is illegal but the laws against it are largely unenforced, and work together with the local authorities to rescue children out of it. In other words, they go in and get the children out. They walk the walk. And it's not just with child prostitution; they get rid of manual slavery, and other forms of violent persecution. The president of IJM, Gary Haugen, has written two books, Good News About Injustice, and Terrify No More. I wrote a review of the second book on the old blog; I might repost it at some point. If you have some extra cash, you might want to consider donating it to IJM. Organizations like this are what money is for.
Second and third are Mercy Corps and Northwest Medical Teams. I know these organizations because they're both based in Portland, where I'm from. They go all over the world getting people the food, medicine, and amenities they need. Ditto with the money thing.
Finally, the Hunger Site. You might already know about this: you simply go to the site, click on the button, and food will be donated (by advertisers) to people all over the world who need it. You can only click once a day. You can make it your homepage to make it easier to remember. If you're wondering whether it's on the up-and-up, here's the Snopes article on it, demonstrating that it's valid. The Hunger Site also has a topbar linking to similar sites, which you can also click once a day, such as the Child Health Site (which donates vitamins and medicine), the Child Literacy Site (which donates books), the Animal Rescue Site (which provides food for abused animals), etc. In fact, I got an e-mail from my mother-in-law about a month ago saying that they were having trouble getting enough people to click on the Breast Cancer Site (which provides free mammograms to poor women). So get to it.
Update: As I say, I won't be adding more ministries to this list, but if you want to mention some in the comments (with links if possible), feel free.