Kiva launched a new model a few years back: KivaZip.org. Like Zidisha, it allows you to make direct loans to underserved businesses. Starting in Kenya and the U.S., you can make 0% interest loans directly and converse with the entrepreneur.
Unlike Zidisha, the repayment rate is much higher (90% ontime repayment on KivaZip vs. a 40% ontime repayment on Zidisha) and Kiva Zip has nearly double the loan volume through which risk management can be refined.
Both models are early stage.
Further, when you lend through Zidisha, there's a chance that you will not be able to withdraw your money (given SEC regulation). Kiva Zip has been cleared by regulators since it does not let you earn a rate of return, but you can withdraw your principal.
Both models are early days, but nonetheless important factors to consider when thinking about Kiva and Zidisha. Want to applaud effort by Paul, YC and the community to direct more talent, energy and resources to great problems of the world.