Dashboard

Dashboard is an application for Mac OS X (starting with 10.4 "Tiger") that allows users to perform small tasks in mini-applications called "widgets". Activated by clicking the icon in the Dock, a semi-transparent layer appears over the desktop and widgets pop up.

Widgets
Widgets are small web pages housed in a .wdgt package that can be created with Apple's Dashcode widget creation software (included with Apple's Xcode, downloadable from here). The stock widgets are: More widgets, third-party developed, are downloadable from Apple's Dashboard Download Page.
 * Address Book
 * Business
 * Calculator
 * Calendar
 * Dictionary
 * ESPN
 * Flight Tracker
 * Google Search
 * iTunes Controller
 * Movies
 * People Finer
 * Phone Book
 * Ski Report
 * Stickies
 * Stocks
 * Tile Game
 * Translation
 * Unit Converter
 * Weather
 * Web Clips
 * World Clock