Here’s an article from MSDN Magazine on building Windows Vista sidebar gadgets - you may find it useful for the contest. They include code samples.

Contents
What Is a Sidebar Gadget?
XML Definition File
The Main HTML File
JavaScript
Docked and Floating
Flyouts
Options Dialog
Reading and Writing Settings
Localization
What Happened to Alert and Confirm?
Debugging
Packaging Your Gadget
The MSDN Magazine Ticker