Chances are you have multiple Gmail accounts: perhaps one for work and one for personal use. Switching between those accounts in your browser can be a hassle. That's where Google Chrome extension Checker Plus for Gmail comes in. Click the Checker Plus icon in your browser extensions bar and you'll get easy access to all of your inboxes in one window. There you can manage all of your emails like you would in a dedicated tab for Gmail–read, archive, delete, or mark messages as spam, or even compose a new message or send a reply–no matter what page you're on. It's the quickest way to check emails without needing to have Gmail open.

Checker Plus Price: Free