rondomusic.net has some nice metal cases with foam inside. you have to cut the foam to fit your mics, but the upside is obviously that it can be customized to your mics.
I got something similar from Fry's. If you go to Lowe's, you can get 3"x3" rubber trim foam for mounting air conditioners in your windows. Pull out the foam-covered wood dividers, then cut the trim foam into strips and you can use that to fill the case well enough to keep mics safe.
It'll take three packages of the trim foam (about $3 each) to completely fill the case, IIRC, though you'll probably only use about two packs if you're storing LDCs because you'll want to leave room for the mics.
I usually avoid Harbor Freight because their tools have a tendency to disintigrate during use, but I have two eyes, so I can afford to have one punctured.