Say that a recipe calls for mushrooms, but you used the last of them yesterday. Key in the word "mushrooms" and the mushrooms page not only lists the many varieties, it also includes substitutes (tempeh, eggplant, bell peppers and zucchini).

Although the site is not completely exhaustive *(or limited to kosher ingredients), it lists about 90 percent of the ingredients you'll likely encounter, including many exotic ones, usually with helpful photos and a short summary of its origin.

The Cook's Thesaurus

Mercola.com