The Crafting Chicks asked me to be a part of their fun Thanks a Day Gratitude Challenge. Thanks chicks! I got to send over a thank you card. Instead of sending a standard one, I made postcards.
I like to order these from Got Print or Uprinting when they have a sale. I can order A LOT and not pay a lot. Then add them to little thank you gifts, teacher gifts, etc.
You could also print these and have guests fill one out for Thanksgiving. A couple of years ago I had everyone who was at my house for Thanksgiving write what they loved about a person and rotate each paper in a circle until they were all filled up.