All 3 of my boys have recently began to collect state quarters. This is a great hobby that is educational as well as fun. They use a puzzle map of the United States to help organize their collections and to check for which states are missing. The boys are very competitive and enjoy trading to expand their collections. They also will raid Mom & Dad's coin purses to see if they can find any "good" quarters.
Our precocious 6 year old announced the other day that Oklahoma was going to be a state soon. He was pretty sure this was going to be the next quarter too.
When I asked him where he got this idea from, he replied, " Oklahoma is the Sooner State!"
Apparently the puzzle has the nicknames posted under the states' names!