Lets you add a custom class to each widget instance.
ZigWidgetClass adds a free text field to each widget control form on your widget admin page. Enter a class name in the box and it will be added to the classes that WordPress applies to that widget instance.
IMPORTANT: It only works with widgets created by extending the built-in multi-widget class! If it appears not to work on a certain widget, that widget is probably not a multi-widget.
Requires WordPress 3.1.1+ and PHP 5.2.4+.
For further information and support, please visit the ZigWidgetClass home page.