If you have multiple shells installed on your Windows Phone/Mobile Device – such as Windows’ own Titanium, Spb Mobile Shell, etc. – and you want to easily be able to switch between them, ShellSwitcher will help you with that.
According to the description, the “program gives the ability to select the native or custom WM plug-ins and activate them on the today screen”. Just run the application and tap on the desired shell you want to switch to from the list of available shells and you’re set. The application is still in beta development so you might occasionally run into bugs but we hope to see them sorted in future releases.
(Source: XDA Developers)