Rated 5 out of 5 stars

This is so useful and well integrated into Gmail that you don't feel like you're using a separate product at all. It's a genius use for the right hand side of the page.

At it's simplest it lets you put a face to an email address. But as well as giving you contextual information it allows you to take actions as well: like follow someone on Twitter, or connect LinkedIn, after you've exchanged emails with them.

This review is for a previous version of the add-on (