Rapportive

This one looks like a very interesting Gmail add-on! Will definitely install this, once I get some sleep. :-/

Rapportive shows you everything about your contacts right inside your inbox. You can immediately see what people look like, where they're based, and what they do. You can establish rapport by mentioning shared interests. You can grow your network by connecting on LinkedIn, Twitter, Facebook and more. And you can record thoughts for later by leaving notes. Imagine relationship management built into your email. For free.

Get Rapportive here