Kiva is a good infrastructure model I believe. I've encouraged one indigenous mission group I support to try to connect with them.
For me, as you suggest, this is best done in connection with the diaconal ministry of the church.
I would like to see something similar done in the US to attack the pay day loan problem. In our county one charges 800% per annum and the problem is excessive demand not too little! I even saw where one advertised a $120 finders fee for "referring a friend".
I've blogged about this topic here:
http://missionlawrence.blogspot.com/2006/10/usury-pay-day-loans.htmlI learned from Chalmers Center at Covenant College (http://www.chalmers.org) about some possible models that do this. They're easier to start than maintain (like everything!)
They're called Community Development Credit Unions. I consider them the US "sister" to microlending and could also work well in conjuction with diaconal ministries.
Keep up the good work Mark.