Armorlite is what i've been using... adds a few mm to each deminsion, but I've dropped this several times and it keeps on ticking... I think this case is awesome.
wish I would have found one for my micro
Seriously the 10 bucks is really worth it. If I ever have to trade it in or sell it, the case itself will be mint, no scratches.
I've been using a MadCatz Game-on case. Works pretty well, and carries games to boot. It does have a couple minor fit problems, but unless you try to open your DS backwards it's pretty solid.
I like the look of the case that comes with the new Pokemon DS Lite. I just wish I could find it sold seperately. Anyone know of a case that is just like it? I don't care about the picture on the case.