Along with grains, legumes make up a large part of my diet. They are a good chunk of my protein intake and my favorite way to make sure I always have dinner on hand. Legumes can also be a cheap main ingredient. This page is a just a start of all the legumes on the market but it's a solid list of what I keep on hand at all times.
For the most part, I always use dried beans and pick up the occasional can when I'm in a pinch. While beans take some time to cook, they can be made ahead and frozen for use throughout the week or month. Each page has instructions for cook time and storing so that you can always be prepared to make dinner.