Writer: Provides a distraction-free writing tool without the use of tools like fonts or bold, etc.
Save to Pocket: Allows you to save articles from WordPress so that you can save and read for later. You must have a Pocket account in order to do so.
Feedly Mini: Feedly helps you subscribe to WordPress articles via RSS feeds. You need a Feedly account in order to use this extension.
After the Deadline: Is an extension that gives you check spelling on the fly while writing your Post in WordPress.
There are many more Google Chrome extensions for WordPress that you can find.
If you’re not a Google Chrome user, there is also some useful WordPress extensions for Firefox users as well:
Scribefire Classic: ScribeFire is a full-featured blog editor that integrates with your browser and lets you easily post to your WordPress blog.