Beans
Canned tomatoes
Canned stock
Cilantro
Cumin
Dried chilies
Hot sauce
Garlic
Limes
Rice
Onions
Potatoes
All of these ingredients are available on your nearest supergrocer's shelves, but you can find them much cheaper -- limes and fresh cilantro in particular-- at a local Latin or Asian market.
For more information on Latin kitchen equipment, such as blenders, metates, lime juicers, and flat griddles, you may want to check out this article on Latin kitchen gadgets.