I use one of these:

http://www.organize-everything.com/dosipiboxwih.html

It's not water-tight, so it should be stored in a plastic bag, but it has a lot of compartments of various sizes, and is overall about the size of an Altoids tin. Not quite small enough for a pocket-size kit, but well-suited to a vehicle or travel kit.

I got mine at WalMart for about $1 each a couple of years ago, but I can't find them there any more, at least not at my local store.