WidgetBox is a great tool that lets you turn your blog or webpage into an embeddable widget. Even put it up on myspace. Customize it, go forth and spread thy widget!
Macophiles have been using widgets for a bit, but in Vista is starting to get in on the action. These mini java hacks are just starting to explode. Blogger is a great blogging tool, because it is optimized for open source edits like Widgetbox.