Here is one I did for my friend's baby shower.
Gallery at Splitcoaststampers
I used a piece of 12 x12 paper. If you don't have any, you can use a reguar sheet of CS. Cut the 11 side of the paper down by 1/2" making an 8x10 1/2 sheet of CS. Orient the paper landscape and fold up the bottom 2 1/4", this creates the pocket that will not be as deep as mine but will be fine. Score but do not cut the folded paper at 5" and 5 1/4', this creates a little wide band that will serve as a spine for your card holder. You only need to do this step if the cards you are putting in are embellished or if you do more than 4 cards like I did, it gives you more room to close it comfortably. Otherwise, just score down the middle. If you want to trim yours like i did with a slanted cut, do so or you can put brads, ribbbons or staples on the corners of the flaps if you like. I used a piece of cs for the latch and used a circle of velcro to keep it closed.
Here is the closed view:
Gallery at Splitcoaststampers