DeLocalizer will remove all non-American English localization resource files that you request.

Localization files provide the language support for an application. All strings of text that an application uses are defined in a localization file. Mac OS X also includes non-English localization files for people who speak other languages. While this is a wonderful technique for easily bringing applications to other languages, it can use up more space than you may be willing if you plan on using no more than one language.