These days there is software for almost every kind of need. So it is with proofreading as well. There is proofreading software available these days by the name of whitesmoke. They claim that it checks for spelling errors, grammatical errors, punctuation errors, and that there is a synonym dictionary and idiom dictionary in the package.
They have separate software for general writing, business writing, creative writing and legal writing.
Go to http://www.whitesmoke.com/ for more details.