In addition to basic cooking tools, you're going to need something to transport your lunch away from home without making a big old mess! I have this set of Rubbermaid containers from K-mart, which I like pretty well, although I don't like to put them in the microwave. I used to microwave them often, actually, but in addition to concerns about BPA and other bad stuff leaching into the food, they just haven't held up after months of microwaving, so I figure it's probably not the best idea.
For items headed to the microwave, I like these glass containers available from The Container Store. They're fairly sturdy (I've yet to break one) and once you remove the lid, they look and act like a regular bowl. If you don't like the idea of transporting glass to and fro, you can always keep a ceramic bowl at your desk and transplant the contents of your meal to it at lunchtime.
For even more lunchtime fun, check out these resources for attractive and convenient lunch equipment:
