Rapportive is a browser extension that displays your social web connections in your Gmail inbox.
After adding the Rapportive browser extension (currently available for Firefox, Safari, Mailplane and Chrome), opening any email in Gmail will display information similar to the example at right in the right-hand margin of the inbox.
Rapportive displays (as available), the contact’s photo, location, title and company, other info from their LinkedIn page. You also get their latest tweets and Facebook posts, as well as a link to connect with them on LinkedIn and a number of other social media sites.
You can even add a private note about the person that will appear with future email interactions.
More than just giving you more context about the person in your inbox, savvy users will take advantage of Rapportive to be more engaging. For example, in your reply you could make mention of a recent tweet or shared interest. Or they might see a follow notification in their Twitter or LinkedIn at the same time they are reading your email reply.
Rapportive has received favorable reviews from The Next Web, TechCrunch, Lifehacker, ReadWriteWeb and others.