Google chrome Extensions 
Chrome Web store 
Wordpress Plugins 
Mozilla Firefox Addons 
Language Manager, Designed to manage language packs for Firefox web browsers this easy to use utility make it easy to manage installed language packs and always have the latest language pack installed.
Automatically switches input language to English when you type in address bar.
Translate English to Japanese.
Select text and press Ctrl + Shift.
Now support only English to Japanese, but I am developing other language support.
Add-on convert highlighted English text to Sinhala Language by using google translator.
S3.Google Translator adds the power of Google Translate’s automatic translations to your browser!
It supports translation of selected text, entered phrase or whole webpage between any of 80+ languages.
New Feature: Language learning!
To see the meaning of a word with the Priberam.pt (Dictionary of Portuguese Language On-Line), consult the conjugation of Portuguese verbs and to search references.
An Extension to type Unicode using the phonetic match on the original keyboard.
DictCn is an online English to Chinese (and vise versa) dictionary extension for Firefox...
Create language learning lessons for your favorite articles online with a few simple clicks. Enjoy rich and interactive content including flashcards and crossword puzzles.
Replaces random selected keywords either for a German or an English text with list of choices.
This is meant to improve your German or English grammatical knowledge.
The language of the Web page is detected automatically.
Shows you a relevant Wikipedia article along with your search results. Clicking links in the article will trigger new Google searches, making it a very useful research tool...
Builds language vocabulary by adding random word translations to pages as you browse.
Translate your selection phraseon any web page in three language English, French and Arabic
