My church asked its members to send each other cards this year. I like sending cards. An invitation to send cards to my brethren is nice. You too might enjoy sending cards to family and friends. For postcards I recommend Dover Publications (http://store.doverpublications.com/). Start at their main web page, type "post cards into the search box. This takes you to the Stationary page, which has a tab marked "card books." You will see the "favorites" list, but you can click on the "View all Card Books" button and see a larger list. They have a nice selection of post cards.
A good source for cards that fold and go into envelopes (note cards) is Pomegranate (http://www.pomegranate.com/). You will have to click on "Shop by Artist" and explore for note card sets. But if you go to Half-Price Books, you can go to their note card/stationary section and you will find card sets from Pomegranate.
The final touch is to go to the US Post Office website and order attractive stamps. An attractive stamp is a nice touch to an attractive note card or post card!
Robert
You might enjoy a related post:
The Joy of Letter Writing September 7, 2015
http://planoparents.blogspot.com/2015/09/the-joy-of-letter-writing.html
In the Plano Parents blog