I haven't started vending, but I've decided if I do I will be using these for at least some of my inventory.
Large Snap 'n Stack Craft Storage Box with Removable Dividers
The trays interlock and you can put dividers in them. The lid has a nice handle for carrying.
They're not cheap, but I figured if I use my 40 and 50% off coupons at ACMoore to pick them up it won't be so bad. I already store some of my supplies in one. On the site I posted you can order extra trays and dividers for the base units.
With 4 cats and 3 kids I'll need something to keep them safe and boxes made from regular cardboard won't cut it!