I made myself an actual "tablet of memory..."
I found this great, free travel tool at the website World 66 which generates a map of states (in red) that you've visited.
As of October 23, 2011, I have visited 27 states, or 52% (The District of Columbia is counted separately). Pretty neat.
You can create your own personalized map of the USA, as well as countries of Europe, Canada, and the world.
Ahh, the delights of exploring our world. As American essayist Agnes Repplier said, "The impulse to travel is one of the hopeful symptoms of life."
(The exercise makes me want to transform the gray states to red...)