I agree that learning from other charities is the best way to evolve. Kiva has a pretty awesome due diligence process that we would like to pick and choose elements from as we grow: http://www.kiva.org/about/risk/kiva-role
The US govt does not do significant oversight of 501(c)(3) organizations. They don't care at all about effectiveness.
EDIT: I dug through the pages and found a link to a Google Spreadsheet doc with basic information regarding the sponsor for each patient. This is one area I would definitely improve into a sponsor link on each patient's donations page. But all-in-all, great stuff!!
Did you get a chance to click on the Medical Partner link on the patient profiles? It opens a lightbox with some info on the partner.
But we'd love to have more robust pages with tons of awesome info (map, financials, photos, data, etc.) for each Medical Partner. We just need to raise the money to pay for the quality dev time we need!