I'm an environmental science student focusing in conservation biology. There are quite a few environmental tourism/fellowship opportunities for those looking to help the environment.
I am actually in the process of applying for an eco fellowship in Australia. I am hoping to get into the Cape Otway Center for Conservation Ecology. If I get the fellowship, I will spend a week at their lodge learning about conservation ecology and working with many unique species.
Besides their fellowship, I know the center does photography tours, and offers other environmental tourism options. There are also many other ecotourism tours, activities, and accommodations all over Australia, and the world. The options in Australia are certified so that you can be sure they are really environmentally friendly.