Earthwatch ( www.earthwatch.org) takes paying volunteers along on a wide variety of academic research expeditions, many of which include projects studying endangered species.

CNN: ASIANOW - TIME Asia | Travel Watch

Supporters tout the valuable research and conservation efforts of zoos, which work with endangered species and serve as more than just a place to see the monkeys on a Sunday afternoon.

BBC: The dual sides of animal captivity

Some of the rest goes on energy research, but that still leaves plenty for pet causes, from endangered species to public transport.

ECONOMIST: Pollution law