Black beans, brown rice, canned green beans, etc.
But here's a few more tips.
1) Oatmeal can be bought in bulk at places like Sprouts.
2) Fruit can get expensive, so I just stick with bananas.
3) Canned tuna is pretty cheap and there's usually sales.
4) Buy the big bulky packages of meat to save money on protein.
5) Quit buying bottled water, it's a waste of plastic and money. I just use the water from my faucet.
Anyone else have any tips they want to share?