Soup or liquidy stew in a thermos or that you can zap in the microwave. Something filling enough to keep you from hitting the vending machine around 4pm ;-) In fact, if you're temped by the chips or whatever at the office, bring something for snack, too, maybe homemade trail mix.

If you slightly undercook grilled chicken breast (or a burger or any other meat or fish), it won't be too overcooked & dry when you warm it in a microwave.

I picked up a small bag of frozen falafel at Trader Joe's yesterday to use for lunch sometime--I'll let you know if I liked it. All I need to do is add tahini sauce and chopped salad (gluten eaters can tuck it all into a pita as God intended!).

Wedge of veggie-laden frittata or crustless quiche to eat cold or warm.

Waldorf salad (I go very light on the mayo and add a little oj, cider vinegar & cardamom). The crunch of apples, celery and walnuts makes it feel like you're getting more to eat.

Variation on the wrap theme: use Ezekiel sprouted grain tortillas (in the freezer case).