This is one of those details that a lot of people don't think much about. At your reception, you will have a gift table, but what about the cards? You will definitely want something to hold the cards, and it is best if it is a container that will hold the cards in securely (so nobody could take one out...). There are a ton of pre-made boxes out there that you could buy, but they aren't usually very special. You could also make something yourself out of boxes etc, but even that can be more work than it is worth (though I have seen some really pretty and unique containers).
For my wedding, I went with something cheap and easy, but unique and beautiful. I used a bird cage. Now, you can buy special "wedding" bird cages, but like all things "wedding," they are expensive and not the best quality. Instead, my mom found a decorative birdcage at TJ Maxx for around $10. You could also look at places like Ross, Marshalls, Home Goods, or even a thrift shop. They are pretty common in the "decor" sections. The one she bought was a copper/bronze color, so we did a few things:
1. Spray paint the whole thing. We decided on white, since it was a wedding after all, and it would match with any decor.
2. Embellish with tulle/ribbon. You do not even need to do this, but it was my kind of thing. I wrapped a bit of white tulle around the top and tied a bow. Then, for my motif, I added a jewel to the middle. We actually used the same bird cage for my sister's wedding, but instead of the jewel I added some black tulle to the top.
3. Set it up on your gift table and wait for the cards to come in!
Here you can see my birdcage on the gift table during the wedding: