Screenshot Plus is a Dashboard widget that can take full screen captures, grab screen areas, and capture windows, desktop icons, and other widgets. The captures support being saved to the clipboard or to the hard drive, or they can be exported to any application directly from the widget.
By default, the app displays a preview of the taken captures. For a truly streamlined workflow, it also offers the option to save or import immediately after capturing; in literally one click, anything on the screen can be ready for editing or stocked away in your iPhoto album. The captures may be saved with .jpg, .png, .tif, .gif, and .pdf extensions.