When we cleaned out the closet recently, we found a boxless deck of cards.  About 10 minutes later, I'd made this snazzy little bag for them.

It's made of one long piece of fabric that has two side seams.  To keep the side seams from poking the cards, I placed a folded piece of card stock in the bag.  The card stock not only protects the cards, but it also makes it easier to get them in and out, because the bag keeps it's shape.  You could totally throw this into your backpack for a day at the park and not have to worry about your cards getting all bent up.

I love little projects like this where you can just crank out the finished piece.  It's nice to not have to worry about perfect seams and stuff like that and just *make* something.