Serious Eats
Budget Bento Ideas
Flickr's Bento Boxes group has a great thread on budget bento ideas, well worth reading if you regularly pack lunches for yourself or for your kids, whether or not they're bento. This tip is pretty nice, especially in this age of hugely oversized meals: "Bento are small - learn to only buy what you need. I actually have saved money on food because I just don't eat as much."