I love this idea I found on Martha Stewart and am going to make one this year to display our holiday cards that we receive.
The supplies are inexpensive and can be found at your local crafts store (even less expensive if you use a weekly coupon!) Using wood glue, affix miniature wooden clothespins to a large (about 14" diameter) embroidery hoop. Alternate clothespins to point outward and inward, spaced 1 1/2" apart. Suspend the hoop from a ribbon and clip your cards in place as you receive them.
Depending on how many cards you like to keep on display, you could have an entire wall of hoops!