Microsoft Translator API

一ヶ月２００万文字まで無料　

参照
http://msdn.microsoft.com/en-us/library/ff512401.aspx

使用可能言語取得

http://api.microsofttranslator.com/V2/Ajax.svc/GetLanguagesForTranslate?appid=[ApplicationID

実行結果

["ar","bg","ca","zh-CHS","zh-CHT","cs","da","nl","en","et","fi","fr","de","el","ht","he","hi","mww","hu","id","it","ja","ko","lv","lt","no","pl","pt","ro","ru","sk","sl","es","sv","th","tr","uk","vi"]

翻訳

URL 

 http://api.microsofttranslator.com/V2/Ajax.svc/Translate

Parameter

 appid   bingで登録したアプリケーションID   access_tokenの指定が必須になったようです(04/17)
            パラメータに指定しても動作しなかったのでヘッダに指定すると動作しました。

 text 翻訳対象文字列

 from 翻訳元言語コード en

 to 翻訳先言語コード ja

contentType text/plain又はtext/html　text/plainでいいと思う