During sabbatical last year, I discovered the Passport To Your National Parks program which is administered by Eastern National.
Each Unit of the National Park Service has one or more cancellation stations that look something like this:
National Park Travelers Club, a club that revels in the NPS units of our nation. There were recently featured in this USA Today article. I soon joined this club and have enjoyed the interaction with others who enjoy the parks as much as I do.
We have now visited 47 out of the 394 units (soon to be 395 with the addition of the Martin Luther King, Jr. National Memorial later this month). This club also offers awards based on your traveling and stamp collecting over the year. For 2010, we achieved the Silver Master Travelers Award level.
Last month, we visited Lewis and Clark National Historical Park on the Oregon and Washington coast and found a stamp that was "Most Wanted" by the club: