Hori 24 game case. These things are smaller than a DS phat, clip closed, store carts 6 per page (4 pages), and generally rock. I've been playing my 3DS a lot ore now I've got 46 games easily available, rather than digging into the "DS Drawer of dooom" which had run out of room, and made it difficult to fiddle around for cases in. I'd dabbled with single hardcases for the carts, put in a tin novelty lunchbox - but even the shuffling/digging through that made a lot of games hard to find.
Original cases are now stored in a box in the DVD closet for (the rare time) when I need to reference the manual.
http://www.hori.jp/us/Products/DS/DS%20Game%20Card%20Case%2024/index.htm
(official listing on the Hori site - this is the DS model, but 3ds ones are much the same)
http://www.youtube.com/watch?v=OIqZHWAxHOg (some dude's video of said product)
They're available pretty much everywhere - get 2 or 3! They're usually less than $10.
I had approximately 20 DS games I hadn't even played yet, and while I still have 19 (I've only had these things a month or so) - being able to see them all at a glance gives me more incentive to play than a drawer full of cases.
