What sorts of containers have been found to be appropriate for storing large amounts of small cards? For example, in Descent: Second Edition, There are 155 cards which must be stored, and which measure 41mm by 63mm. Once they are sleeved (in these), they no longer fit in their little baggie; is there some company that makes/sells boxes that fit these small cards? Are there any commonly available containers that work well to fit these card sizes?
I usually use those white cardboard boxes to hold large amounts of cards. They come in various sizes. http://www.amazon.com/BCW-Count--Corrugated-Cardboard-Storage/dp/B000K3XQ8U/
Or I create my own boxes using plastic canvas. (sorry i do not have any better links for these at the moment) http://www.crafts-for-all-seasons.com/plastic-canvas-box.html
You can get little plastic boxes in all kinds of shapes and sizes.
Also the little clear plastic bags with press-in tops (known as zip-lock)
For storage of multiple card-based games there are all kinds of small craft storage units with drawers of varying sizes. Personally I use the bags for games with lots of elements such as Agricola, and just keep all the bags of pieces/cards in the Agricola box.
Magic: the Gathering fat-pack boxes are excellent for storing multiple cards in (I have a friend who stores Race for the Galaxy, Gloom, The Great Del Mutay, and some regular playing cards in one) You can get empty ones from ebay or M:tG stores such as Troll and Toad (I'm limited to 2 hyperlinks).