Tempeh is the heartier, lesser known sister of tofu. Also made from soybeans, tempeh is less processed than tofu. In fact, the soybeans in tempeh are fermented and used whole, versus tofu which is made from soy milk. Tempeh contains more protein and fiber than tofu, and more calories.
Tempeh has a nutty flavor and can be bitter if not prepared correctly (try steaming it first to rid it of any bitterness).