My local Walgreens has a film processing counter... the kid who works back there will give me a box full of canisters for the asking. "We just throw them away."
I use Coghlans and Nalgene canisters for a lot of things. I also use prescription bottles, especially for vaseline-impregnated cotton balls for tinder. I like used spice containers for things like salt and sugar for a weekend. Cinnamon works best, imho, with little residual taste or smell... pepper, nutmeg, and allspice all leave a strong smell. Old parmesan cheese, mayonnaise and peanut butter containers work well for larger quantities.
Altoids, Fisherman's Friend, and Sucrets have good metal tins. Altoids Smalls come in a REALLY small tin. Mentos candies come in a nice plastic container. My mom gave me some sort of glucose-tablet container once that I use for a hiking-sized repair kit, much like a prescription bottle.
I have a really cool old brass film canister with a finely-threaded top (not the normal pot-metal film canister with screw-on lid), but haven't found a use for it yet... those you find on ebay... they also sell 16mm film canisters, roughly 1"x 4", but they're not cheap.
Plastic travel soap dishes make good containers for things like First Aid Kits and Repair Kits.
In the Army, we had something called an M256 decontamination kit (with the BLUE training inserts (alcohol pads), not the GREEN real decon solution pads). It was a roughly 2x3x4 container with a gasket-sealed lid and a strap that kept the lid and body together, with a hook on it... these are nice and waterproof, but heavy.. I have one, but still haven't found a use for it yet.