If you're really concerned about the environment, consider making the Brooks Trance 8 Biodegradable Running Shoe ($140) your next fitness purchase. These sturdy running shoes feature a foam midsole that biodegrades 50 times faster than conventional athletic shoes, by using molecules shaped to let the bacteria found in dumps decompose them more easily. Other features include a moisture-controlling Element mesh upper, rear and forefoot HydroFlow cushioning, and looks that won't embarrass you at the gym.