Source: Linguix Free Writing Assistant
Linguix is a grammar checker and more that is available as a Chrome extension and a website. As a Chrome extension, it is available for writing on various websites. I’m currently using it in the WordPress editor as I write this post.
The extension and website do require an account to use. This is relatively painless if you are a Google school since Google logins are available.
Besides checking your grammar, Linguix has some pretty cool other features, such as creating shortcuts to longer phrases.