Budget-Friendly Meals?

A bag of couscous, if bought in bulk, can be very cheap and will go a long way. Same for dry beans/lentils/peas. You can make soup, curry, stew with these for very cheap. Add broth, vegetable and favorite dry items, let cook for a while and eat. It's easy to make many different flavor.
Eggs can be cheap as well and eaten in a variety of way: Sandwich, omelet, hard boiled, etc.
Veggies, depending where you leaves can be cheap. Couscous, tomato, cucumber and feta is a good lunch that will be very cheap per portion.

The pricing may vary depending on your location but I will reference for the Pacific NW and shopping at the local Winco.

Dozen eggs - $2
Bag of lentils - $1
Carrots - $1
Onions - $1
Potatoes - $2
Broccoli - $3
Bag of in-season fruit - $5
Head of lettuce - $1
Kielbasa sausage - $4
Package of boneless skinless chicken breast - $5 or rotisserie chicken
Bread or pitas - $3
2 cans of tuna - $3

I'm assuming that you have some condiments at home like butter, jam, mayo, bouillon cubes, salad dressing etc.

You could make eggs for breakfast with toast. Lunch could be tuna salad sandwiches or a green salad with a scoop of tuna on top. Grilled or baked chicken with steamed broccoli or you could do stir fry for lunch or dinner. I make a soup with the lentils, kielbasa, potatoes, carrots, and onions which can last for 3 days - very hearty and filling. I also freeze the bones and vegetable peelings to make chicken stock - it's cheap, low in sodium and tastes better than the canned stock.

someone posted this pdf cook book yesterday. it's called 'good & cheap.' i haven't looked all the way through it, but it looked like it had some good ideas

https://8b862ca0073972f0472b704e2c0c21d0480f50d3.googledrive.com/host/0Bxd6wdCBD_2tdUdtM0d4WTJmclU/good-and-cheap.pdf

Check out budgetbytes.com

The recipes are relatively healthy, though not necessarily "diet" recipes, and sometimes I go through and cut out some of the carbs and oil and double up on veggies. Never made anything bad off that site though. Because it's budget-friendly, I usually have most of the ingredients on hand (no need to go out and buy some fancy ingredient you only use for 1 recipe), and it's usually easy to sub something out if necessary.