I like to make bean soups (black bean and 12 bean are both popular at my house) and serve them over rice - filling and a decent source of protein, plus great as a repeat meal. I'm not a vegetarian, so I make them with chicken stock/broth, but if you're watching the sodium content, I would imagine you could substitute water for stock fairly easily.
I also make a bean-only taco filling - I google for a taco mix recipe that looks good and matches the ingredients I have in my pantry, and then instead of making it with ground beef, I just use an equal amount of canned beans.
My mom does something similar when she makes chili - she replaces half the recommended quantity of ground beef with an equal amount of kidney beans (I know it breaks the no beans in the chili rule, but it tastes good!)
I also eat a lot of breakfast for dinner (but it doesn't leave good leftovers) - things like omelets and scrambled eggs, especially served with hash-browns, tend to be filling and meat-free.