Started the business Christmas letters last month. Close to 150, all handwritten with a short note depending on the business relationship. Hard part is catagorizing the customer on which type of card he/she would like (comical, religious...). When I'm out visiting customers during the holidays, all I ever see is the same dull, "safe" Christmas card with the company name stamped on the inside of the card, and if you're lucky, people (employees) will sign their name to the card. That just seems so impersonal to me that I don't know why they even bother sending those cards out.
Wife does the "family story" for the year, usually with pictures and sends them out to everyone (for family and friends).