Translate Extension for FireFox

Mozilla Update :: Extensions -- More Info:Translate - All Releases

"Small extension that either translates: web pages (via toolbar button) or selected text (via context menu) from several foreign languages into English, as well as 12 other languages. Uses BabelFish and Google translation engines."

Instructions:
Tools -> Translate -> Select Source Language
OR
Select Text -> Right Click -> Translate -> Select Source Language