I find that I usually have some kind of salad or some kind of chicken.
I buy boneless skinless chicken breasts when I can get them on sale. I grill them a few at a time and keep them in the fridge. Then for lunch, I slice one up while it is still cold, put a tablespoonful of pesto over the whole thing, and stick it in the microwave until hot. Add some brocolli (or not) and lunch is ready!
I also make casserole type things on occasion. This is great because they will last for several meals, and can be microwaved.