Rated 5 out of 5 stars
While this add-on is still under development, it gets better with every release. This add-on checks your writing and stays out of the way.
After the Deadline is the proofreading technology used on WordPress.com. Why do you want it in your browser?
The spell checker uses context to generate suggestions. It smartly suggests the word you intended.
This add-on looks for misused words. Do you know when to use affect or effect? Misused words account for 1/3 of all writing errors. No other browser-based writing tool finds these.
This add-on also checks your writing style and grammar. Silly typos and tense errors are found with ease. This add-on also has an option to explain your errors to you.
This add-on will make you a better writer.
[ Disclosure: I'm the developer of the After the Deadline server-side technology ]