This freeware let's you create widgets for your Windows or Mac:
Amnesty Hypercube is more than just a new desktop widget platform.
It's also the easiest way to collect, manage, share and publish "web widgets" -- snippets of code meant for your blog, home page or MySpace profiles.
Already using Sidebar? Any widget in Amnesty Hypercube can be pushed into your Sidebar with one click, which makes it a perfect extension to Vista's native widget environment.

Full story:
http://www.amnestywidgets.com/HypercubeWin.html