The original suggestion I am sure many of us have heard, but using Word is a great idea. Also, Whitesmoke sounds great!
I'd suggest also throwing into these sites to get a bit more readable and also unique.
http://www.spellchecker.net/spellcheck/
http://www.languagetool.org/
http://www.abisource.com/
Takes a minute more, but I just did it with 10 articles over the last 15 minutes and it came out better.