YOXI  This is a very handy app if you want people to have access to an app in different languages without fiddling with the system prefs each time - one improvement I would suggest to this plugin is to have it actually check whether the language resources are actually present in the .lproj folder - some apps have empty .lproj folders, so the plugin shows such a language in its 'available' list but then throws up an error message when you choose it. It also took a couple of restarts of Finder after installing this before my Finder behaved properly again, but who knoweth what caused that.  
(Version 1.0)