Nothing takes the place of actual feedback on your writing. You should know that feedback generally involves three stages from the initial impression of the manuscript, to plot, theme, and other elements, to the final stage of grammar and punctuation.
This is where I like Paperrater.com. Don’t get me wrong- no program really offers 100% accuracy in this area. Why? Mainly because it doesn’t recognize that sometimes, its ok to break the writing rules. Sometimes, its okay to use passive voice, or slang, or informal language.
As always “Know the writer’s rules to understand when you can break them”.
That being said, the site offers a nice FREE service where you can cut and paste large section of writing and have the service rate it. You get a handy report that breaks it all down as well.
I’ve looked at a site called grammarly.com as well (which seems to be down right now), but I find their free version limits the words you can have checked, and then you find fees start to accrue.
Post in comments your thoughts on automatic, robot-driven paper checkers, or your own experiences with this type of service.