Elephant Trekking in Northern Thailand
http://www.youtube.com/v/wOnz3fWa8O4&rel=1This was a very uncomfortable experience!
The ethics of it are debatable too. On one hand, they stopped logging in Thailand and using the elephants for tourism is certainly better than letting them die. On the other hand, the place I went too seemed to be breeding them too, with no signs that they were to be re-introduced into the wild.