The eXtro TemplateSwitcher allows you to display a list of available template styles in the frontend.

By clicking one of these styles, the respective Joomla template will be activated.

Of course you can define which template styles will be available (in the backend), this prevents templates from being displayed which are eg still being developed.

Update:
TemplateSwitcher V1.1.1 resolves a small issue related to jQuery , and adds an additional rotation effect to the Modules open/close trigger.

Update:
Template Switcher V1.1.3 now also uses the Joomla Updater!

***** NEW Template Switcher V: 1.2.0
This new release improves compatibility with PHP 5.4 and J3.x, makes the module overridable and adds a additional (nicer) style to the TemplateSwitcher Trigger.

Template Switcher V1.2.1 improves compatibility with PHP 5.4 and J3