Christmas carols cards are quite popular as they add a religious touch to the sending and receiving of cards. These cards have famous Christmas carols written on them. There are two -three lines of the carols written so you can choose the card which has your favorite Christmas carol written on it.
There are also Christmas carol cards which not just have the carol written on it but also has a background music playing which happens to be the tune of the carol. These cards bring about a musical touch to mailing e-cards.