I've just bought a Kindle 3. It's a lovely device, light, nicely shaped, a superb screen, and I think I had it two hours before I jailbroke it so I could run my own software on it.
This page is a collection of some of the stuff I've done with it, and the things I've learned while doing it, and some of the crude but useful tools I made to do it with.
Getting started with Kindle development
This is a brief guide on how to get set up running programs on your Kindle, including the tools I put together to make things easier, and a useful stub application for use as a starting point.
A Javascript shell for the Kindle
The above document actually resulted from this project, which is a port of Rhino as an interactive Kindle application.