It is specifically built for your Gmail account. With it, you can write an email and then schedule it to be sent or returned at a later date. You can track messages to make sure that you hear back, and schedule reminders right inside Gmail. Boomerang also helps you postpone incoming emails, by making them disappear from your inbox into a specific folder or label.
Grammarly is a free widget that will check spelling and grammar on just about everything you write. It can be an email or a Facebook/Twitter post. For a fee, you can upgrade your account and check for plagiarism and look for better sentence structures.
With this extension, you will see inspirational quotes whenever you open a New Tab on your web browser other than the bland that most browsers display. You will also get to create a to-do list, check the weather and set a daily focus reminder to help organise your schedule.