The Sidebar in Vista is a dock for small, lightweight applications that provide useful information at the user's fingertips. There's a growing community creating all kinds of gadgets from Virtual Earth maps to eBay searches - all these are downloadable from the Microsoft Gadget Gallery online. Here, you can find both gadgets that you can use in Vista's sidebar and also on www.live.com to personalise your online page.
In the future we're going to see the line between live.com and sidebar gadgets become blurred with the ability to get your live.com gadgets on Vista and visa versa.
Back to the sidebar, the business value is realised when applications provide their own Sidebar gadgets to provide a window into critical information relating to the everyday work and role For example, applications like Microsoft Dynamics CRM will soon ship with Vista Gadgets that allow quick access to business critical information like sales orders and customer data.
In the screencast I've recorded below, there's a Virtual Earth gadget that provides the user with the ability to find and locate addresses and places very quickly indeed.
To find out more about Gadgets and how to develop your own check out the following resources: