[photopress:preview1.gif,thumb,alignright]Alessandro Crugnola aka Sephiroth just released great new Firefox extension for Flash developers. The extension comes with all currently available Flash player plugins (from the v2 to the most recent 9,0,16) and allows you to easily switch from one plugin to another, or also to remove the currently installed plugin (eg. for testing the express install feature).
Permalink to the post on his site.