I used to put a little hole in the corners and string them all on curling ribbon. Then I would tape the ribbon ends to the wall and curl the ends. Looked very pretty, but it fell off a lot. Then we tried card holders, but I couldn't see my cards well enough -- might as well have them in a box! Then we tried taping each one individually around the door frame into the family room. This looked nice, but all that tape!
Now we just stand them up on a big bookshelf in the LR. We don't get as many anymore, so it isn't as hard to display them.