Read all about seitan and how to make in this article from the Vegetarian Resource Group. Tempeh is a cultured soybean cake with a firm texture. It tastes great marinated and grilled. Tofu comes in various textures from silken to extra firm and each can be used in infinite ways. For example, silken tofu can be used to reduce the amount of egg used in recipes - or, use it in place of sour cream or yogurt.
Soy milk is a great substitute for cow's milk as a beverage, in cereal or in recipes.
Miso is a paste made from soybeans that tastes rich and salty. You may have tried it made into a soup in a Japanese restaurant. They're so mainstream you can even get them at Starbucks. Used under License.