Paypal just did a 100% match offer for $25. You loan out $25, they give you another $25 to loan. Theoretically, if you get your loans repaid, you double your money.
I saw lots of microloan stuff in foreign countries to do stuff like buy seed to launch a farming business, buy fabric for a clothing store, etc. I was able to find an American business looking to start up, but those are rare.
Cons include: You don't make any interest on the loans. Some of the loans are never repaid. They work hard on their site to get donations, increase your loan with a gift, or re-loaning the money you get back.
At best, I think it's something you do as a charitable gift/writeoff. I'd assume there's a fair chance you'll never see the money again. My loan was for 24 months, we'll see how it does.