I premake a big soup.
Beef (often the morningstar crumbles which have less fat then ground beef), broth, whatever veggies, either fresh, canned or frozen, and sometimes lentils or rice. I also like chicken, broth, veggies, rice or pasta. I make a huge pot, eat some that night. Then let the rest cool.
Then I take the small round reusable ziplock containers. I fill them about 3/4 way full. Usually 5 or 6 servings per pot. I then freeze these. When I need a quick lunch I grab one from the freezer, let it sit on my desk in my lunch bag for the morning and then nuke it for 3-5 miuntes at lunch. Very quick, easy and frugal. Just remember to make water/broth based soups, load up on the veggies and use lentils/brown rice/smart pasta for the most health benefits.
I take a few crackers or a slice of wheat bread and it's a really nice lunch. I also take fruit juice/fruit, and some kind of dessert (cookie or pudding) to round out the lunch.
eta: I've taken hummus and cucumbers on wheat for lunch as well, but it didn't seem to stick with me, as well as Peanut Butter or veggie soup. Don't know why. Hummus is a favorite for my snacks. Either with cucumbers/bread or on crackers/celery-carrot sticks as a dip.