Ok, this is really brilliant.
This is cool for at least two reasons: (1) a great way to combine an addictive game like Tetris with something everyone tries to learn at one time or another – the 50 states (or countries in other versions), and (2) a great example of something that could not be done in “just a web page”.
The states fall from the top, just like the blocks in Tetris, and you need to use the arrow keys to move them left and right (and/or speed downwards). I made 5:17 on my first try (fumbled a few). We need more examples like this.