I bring my lunch + snacks to work pretty much every day. I have more than a dozen different lunch bags and containers, but my favorite for traveling by bike is the Tupperware Lunch'n Things container. The slim size and shape is perfect, and it's leak proof. I've dropped mine many a time, but no food has ever leaked from one compartment to another. I just toss the container in my bike basket on top of my other stuff and off I go.

Bike to Work: Loaded Basket by drv1913, on Flickr

I have a couple of insulated lunch bags, but I have them because they are cute, not because I feel the need to keep my food at a certain temperature. I never, ever put food in the office fridge. I just keep my lunch at my desk until I'm ready to eat, and so far, I've lived. I avoid using microwaves, so if I really want a hot meal, I use my stainless steel Thermos and just stuff that in my bag along with every thing else. My cutlery, bandana/napkin, and glass straw live in my bag all the time.