How to “Jailbreak” Your Kindle for Custom Screensavers and Fonts
Note (May 31, 2012): This was accurate as of April 2011, and may not work on the newer Kindles. I used this information to get custom screensavers on my Kindle Keyboard (as it is now called).
Note: This applies to the Kindle 3 running the latest software update, 3.1. For Kindle 2 and Kindle 3 running pre-3.1 software, see the Mobile Read forums or wiki.
Download the Jailbreak Here: http://yifan.lu/p/kindle-jailbreak
Follow this guide to get custom screensavers working: http://wiki.mobileread.com/wiki/Kindle_Screen_Saver_Hack_for_all_2.x_and_3.x_Kindles