Ask HN: As an engineer, how can I volunteer in the developing world?

I'm an experienced software developer from the states, but I've spent a lot of time overseas, particularly in Asia. I'm interested in spending some time, at least six months, volunteering in the "developing world", for lack of a better term. Are there programs or organizations that I should be aware of that will let me use my skills to help others? How can I have the biggest impact?

No particular preference - I'm fairly comfortable in South East Asia already, so that would be slightly easier - but anywhere would be fine - Africa or Central America seem like good options as well. I just can't seem to find any established programs that let me donate my skill set anywhere. It's really surprising. I'd be happy to pay airfare and, assuming it's affordable, my own room and board.