I am signed with a unique system that i can use my handwriting, a personalized card, option to choose 1000s more cards, and send it to hundreds of clients with one shot for about $1 per card, including postage. The clients gets a personalized hand written card that makes them feel special.
Even with some of the close clients, i know their anniversary and Birthdays which the system automatically reminds me.
I haven't sent any cards this year but previous years I sent cards 4 times a year and it has worked with return business.
Be kind to your neighbor, he knows where you live