right now i don't have too too many blades, and they are all users. the ones that aren't laying around because i'm always grabbing them go into a small 3 drawer tool case with a lid. i keep blade blanks and short pieces of steel in the top lid area.
folders in one drawer, fixed blades in another.
in the future, especially if (when) my collection grows, i intend to get a larger tool case like the one i have and put nice cloth liners in the bottom of the drawers. use some of those silica gel packs in each drawer. i want to have enough room for the fixed blades, machetes and hawks/hatchets. on second thought, maybe i should get one of those pelican rifle cases...
but i would say keep them oiled if you aren't using them often, keep them together (except for the stashed ones in bags etc) in a drawer or in a bin (those rubbermaid bins are good as suggested before...) and don't store in leather sheaths...i've never had a problem even in my damp basement, but better safe than sorry.