Even if you've worked to make your brown bag lunch more appealing, sometimes the biggest drawback to the brown bag is that you just want a warm meal. That' where the office worker's portable solar oven comes in.
If you're of the microwaves-be-damned, I-want-to-do-it-myself school of thought, Instructables user z0rb details how to make a portable solar oven while "keeping with the grand tradition of creating ways to warm my lunch at work with readily available office supplies" — namely a cardboard box and some tinfoil.
We've featured a couple of different solar ovens in the past that'll probably get you a lot better solar cooker, but it's still a fun and clever idea, and you can probably put it together with supplies you've already got around the office..
The Office Worker's Portable Solar Oven [Instructables]