[pjbrunet]

Have you tried Rapportive? https://rapportive.com/ It shows additional information about the person in your Gmail sidebar.

Also you might want to check out Nimble, like Rapportive it pulls info from other social networks. If there's a feature you want, it seems they listen to ideas.

I've also used http://www.cerberusweb.com/tour for sorting email and importing additional data about people, but that might be overkill. With Cerberus you would have to import the location data info yourself, for example. It's a "power user" type of application, very versatile.