Here’s a list of tips, tricks for the Amazon Kindle. These have been checked on a Global Kindle (software version 2.5) They may work on the original Kindle and Kindle DX and the new version 3 UK Kindles.
Keyboard Shortcuts: For a quick game, press Alt+Shift+M – Start a game of Minesweeper. While in the Kindle Minesweeper game you can press G for a version of “Reversi”

To take a screenshot: Alt-Shift-G – Take a screenshot of the currently displayed screen. A .GIF file will be created in the \documents folder (plug the Kindel into your computer to see them).

Hope this adds even more to the entertainment value of your Kindle.