Here are some of my low-cal favorites:
Tilapia filets, bought individually sealed, dipped in shake'n'bake (for pork) and sauteed. I put it on a griddle.
The same would probably work for chicken.
I have a daily strawberry smoothie at lunch: about 8 oz of frozen strawberries (get mine by the 4lb at Kroger, not exactly cheap), microwaved for 30 secs, blended with 8 oz skim milk and 2 packets of sweetener.
Any of the lean Michaelina brand frozen entrees. I eat them over about 8 oz of defrosted mixed veg, such as Kroger-brand Italian, Asian or California-style. I can't say if they're all that healthy -- I don't check about preservatives, and some of them are a little sweet, but the calorie count of the entrees are all under 300, the vegetables lower the calorie density, and they mostly taste pretty good.