In November there were reports of an upcoming Apple development tool for creating Dashboard Widgets. The new application was called "Dashcode". A few screenshots circulated around the web, with no details on release timeframe.
The Dashcode application now comes with the Developer tools that accompany the MacBook. One user posted screenshots of the application.
The application can be found at in /Developer/Applicatons after installing Developer Tools which accompany the MacBook or MacBook Pro. It does not appear to be included with the latest downloadable version of Developer Tools.