The creators Andrew Bullock and Megan McGuirk both decided one day that people who really want to type 1337 have a hard time doing so, and that people who don’t know what it is need clarification. So they decided to create a keyboard layout that will type in 1337 speak for you! The characters of 1337 become corresponding with the keys you type on your computer. In addition to the fact that you can speak in 1337, you can easily switch back and forth using Windows XP’s Language Bar.
Check out the download page and the installation / usage page for more information.