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I use white smoke its a good site for correction / grammer
http://www.whitesmoke.com/free-online-checker
I usually use google translate or office default checked. how ever googling any wrong word would suggest correct alternatives i use this for spelling:D
I don't konw but maybe these apps will help you http://learnenglish.britishcouncil.org/en/apps
For ceorrection? Buy any English course book like Grammar or Lexics in Use, with a CD, the CD usually contains tests which will be swiftly checked by the prorma when you've done them