Here are my questions. They're kind of specific to the reason I'm interviewing this person, so they might not be a whole heck of a lot of help, but hopefully they get you something:
1. How did you decide to help in this cause/make this your calling?
2. Have you experienced much opposition from people or circumstance?
3. How has seeing another part of the world affected you as a person?
4. Was it/Has it been difficult to keep up your motivation to take on such a big task?
5. Where do you see this project going in the future?