If you create separate satellite assemblies containing your language resources placed in subdirectories named after specific cultures, the ResourceManager will load the right resources based on the value of the property Thread.CurrentThread.CurrentUICulture.  That way you can add new cultures by just adding a new satellite assembly without recompiling the main assemblies

Read more here: http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpguide/html/cp
concreatingsatelliteassemblies.as

I hope this helps you

Regards, Jakob