Rainmeter is a desktop customization platform. Through Rainmeter, you can enhance your Windows computer at home or work with skins: handy, compact applets which float freely on your desktop, much like Windows Sidebar gadgets, or dashboard widgets for the Mac. Rainmeter skins provide you with useful information at a glance. It's easy to keep an eye on your system resources, like memory and battery power, or your online data streams, including email, RSS feeds, and weather forecasts. Many skins are even functional: they can record your notes and to-do lists, launch your favorite applications, and send your tweets to Twitter - all in a clean, unobtrusive interface that you can rearrange and customize to your liking.
Thanks to ARMOUR for the update.