Indonesia, Thailand, Vietnam, Cambodia and the Philippines are the countries I'd recommend in Asia. Cheap rooms, good food, beaches, culture, etc.

In South America, I'd say check out Argentina and Peru. Costa Rica and Nicaragua are my favorites in Central America. Prague was nice when I went a few years back, and not as expensive as other European countries. I'd like to check out Poland, and some other east block countries. I'm not sure how expensive they are these days.

If you can afford it, I'd take more than a month. Take a couple of months, or come back when you don't feel like traveling any longer.