Every December, Zack and Hilary Rudman used to send out nonsectarian cards with winter scenes and generic holiday greetings. Now, however, Zack Rudman, a Kansas City lawyer, has found a variety that seems to better suit a Jewish man and an Episcopal woman with two young children as familiar with the menorah as with a manger scene. These cards proclaim: "Merry Chrismukkah!" "I'm all for holiday cards but I want to make sure when we send something it respects both sides of our family," Rudman said. "I always like to deal with religious differences with humor. These were right up...