One of the fun things I've done to my Christmas cards in years past is to send them to Noel, MO for a special holiday postmark.
This is an easy way to add a little detail to your cards when you send them. All you have to do is address and stamp (very important!) each card. Then you package them all together in a tear-proof manila size envelope (you can get these at the post office) addressed like this:
Noel, MO 64854
I think it cost me around $7.00 last year to send my envelope of 75 cards to Noel for the postmark. Not terribly expensive!
For a listing of all the 'holiday towns' in the United States and their zip codes, you can go to this website. Now that I know of other places with great postmarks, I'll try a new one this year.
My tip: A good way to see what the postmark looks like on your envelope, and to know when others are 'receiving' your cards, is to address one back to yourself.
This also adds a fun touch to your scrapbooks if you included the envelope (that you addressed back to yourself with the great postmark) along with your family Christmas picture on your scrapbook page.