From the blog of Nicholas C Rossis:

If you’re anything like me, you have already installed Grammarly on your computer and use it to make sure those pesky commas and prepositions are all correct.

However, editor Mary Walton recently alerted me to not one, but ten alternative tools that you can use to make sure your writing is as flawless as possible!

I hope you find her post as useful as I did.

Source: 10 Proofreading Tools For Writers: Guest Post by Mary Walton