This was by far the biggest missing feature from Rapportive, which is already one of very few free services I'd pay for. In addition to just seeing the sender'

This was by far the biggest missing feature from Rapportive, which is already one of very few free services I'd pay for. In addition to just seeing the sender's photos, LinkedIn title, recent tweets (hover to see whole thread), etc. in the sidebar, if you hover over any email address inside the email (e.g., anyone cc'ed) it'll instantly display the information for that person as well. I don't ever keep Twitter open (maybe I'm in the minority here) so even if you only email friends, it's nice to see what they've been tweeting when replying to their email. But if you often have people you don't know showing up in your gmail, it's a must-have