I own (don't currently use) the case Reverhart is talking about, it could hold close to 100 decks.
If you're just needing storage you could also get a clear plastic tub from wal-mart, try to find one that isn't that deep but has a good length/width, it'd be cheaper and could hold a lot of cards.
I plan on getting a smaller case and using it as a close-up case, the one everyone uses is more than I need for traveling my usual set. I believe Vaultz makes different sized cases for many different purposes.
I always thought a library card catalogs would be nice card holders, but I'm not 100% sure and they're expensive new.
Demco! and I never run into them used (at least, not smaller ones...I don't have space for a large one).