Active Inbox for Gmail
Use your Gmail as a serious system for tracking everything you need to get done with this free add-on.
Email is a terrible system for digital communications — it just happened to get here first, so everyone uses it. If you're stuck with an inbox that is slowly rotting your brain, here's a fantastic free extension for Gmail that can help you get back on track.
It's called Active Inbox, and it adds some really smart email-management features to help you get your priorities straight and get the junk out of the way.
Once installed, it helps you sort out what needs to be dealt with quickly and what's next on the list, and improves the overall interface, so you can sort emails into project reference buckets and to-do lists.
A paid upgrade lets you add deadlines to emails and add private notes for your own reference. If you like Getting Things Done, Active Inbox could change your email life.