The Yahoo! Widget Engine is a JavaScript runtime engine for Windows and Mac OS X that lets you run little files called Widgets that can do pretty much whatever you want them to. Widgets can be alarm clocks, calculators, can tell you your WiFi signal strength, will fetch the latest stock quotes for your preferred symbols. May be a strong marketing tool, too. Widgets are waiting to be discovered by marketers. Content in widgets come directly to their desktop, bypassing e-mail. It's one way to combat a decline in e-mail open rates.

For example, this widget is car rental wigdet. On customers' desktop and directly... It is an easy one-click way to compare prices and availability on over 40 car rental companies at every city and airport in the world. You can specify any brand or class of car to include in your search or even the "Best Buys" for each company.