Exchanging postcards is an activity packed with learning. Kids can improve writing skills, learn geography, math (buying stamps and making change), and how the postal system works. We've been exchanging postcards on and off for a while now and the kids have built up quite a collection. A while back we participated in an organized 50 state postcard exchange. We have done informal exchanges through Postcardkids and PostCrossing and have purchased many postcards during our European travel adventures.
In organizing the cards my daughter received a geography lesson and an alphabetizing lesson. She had no idea she was receiving the lessons, she was just busy organizing.
The postcards were stuck to loose leaf papers with photo corners in a notebook. The notebook contained tabs for each of the continents as well as a separate tab for the United States. The first sheet behind each tab was a blank outline map. Behind the map was a sheet for each state or country in alphabetical order.
To put cards in my daughter had to find the correct page. Since the book was in alphabetical order she quickly learned how to alphabetize. In addition, as each of the postcards was placed in the notebook the country or state where the postcard originated was colored.
Here's the Missouri page.