Dashboard
PowerTunes provides a Dashboard widget that lets you quickly open up any of your iTunes libraries without needing to open up PowerTunes first. To install the widget, just select "Install Dashboard Widget" from the PowerTunes menu in the menu bar.
The widget is fairly simple, providing a pop-up menu that lists all the libraries you have in PowerTunes. If you select a library from the pop-up menu, your Dashboard is dismissed and that library will immediately be opened up in iTunes. PowerTunes does not need to already be open for this to work, and the widget will automatically detect any changes you make in PowerTunes to your library list, keeping its pop-up menu up to date. Note that any libraries for which the library file cannot currently be found (e.g. libraries stored on a hard drive not currently attached to the computer) will not be included in the pop-up list. Also, as a shortcut, double clicking on the PowerTunes icon on the left side of the widget will open up PowerTunes itself.
The PowerTunes Dashboard widget can be uninstalled the same way as any other widget, using Dashboard's built-in widget manager.