Right now, when you sign up (which requires nothing more than an email address or a facebook account) you can loan $25 for free. This means $25 will be loaned to someone and will not come out of your pocket.
Kiva loans have a 98.93% repayment rate. How amazing is that? So your money is not only doing good, you're almost certain to get it back.
There are so many people who need help, I had no idea how to decide on one. I finally went with this woman in Kyrgyzstan for the silly reason that I like dumplings ("she works in a factory that makes dumplings"). All of them are good causes, so no matter who you help, it's a good thing.
Now that I used my free one, I'm looking for someone else to help. It's a pretty cool feeling, knowing that I can help someone. Not some generic group that's aiming to help poor people or animals or whatever, but to know the person's name and why they need the money. It makes me happy.
Edit: Okay, second person, lending out of my own pocket, is this person, in Benin (Africa). :)