I second the crockpot idea! I put a coupel boneless skinless chicken breasts, a small jar of salsa, and a can of black beans in the crockpot for 5 hours and then drain it and shred the chicken - it's good for wraps/buritos or on top of salads. I can eat it hot or cold. Keeps well in the fridge.
I'm also a huge fan of just opening a can of good quality tuna (drained) on top of a big salad. Quick, easy, healthy.
I make a carbonara
which would be a single meal if I didn't add a HUGE pile of veggies to it. Then it turns into a dinner and a cold pasta salad for lunch the next day. It is perhaps my favorite food (it has bacon in it so right there it moves up the list!) and it really sticks with you - you aren't hungry for a loooong time after that. (it's very fast and easy to make, too - 10 minutes from start to sitting down to eat)
I make a crustless quiche that's fast to make but it does have to cook for 20 minutes in the oven. But it's another one of thos things that is good cold or reheated the next day.
Mostly I cook on one day and live on leftovers the rest of the week....