Rapportive is a great browser enhancement for Gmail. It automatically looks up email addresses and populates a sidebar with that person’s profile photo (from Google Talk or Flickr), job title (from LinkedIn), tweets, as well as links to their profiles on Facebook, Skype, etc.
I find it especially useful when reading mailing list messages, as itÂ lets me easily find the twitter accounts of interesting people.
It’s also useful for making you think critically about the information you have exposed online. By looking at your own profile, you can find out if there’s any information that you are exposing without meaning to. In my own case, I was surprised to see my ancient Flickr account from circa 2003 on it which I’ve since made private.
I think it ties in nicely with IBM’s recent study that 21% of email users would consider applications to complement email. Lotus is also cooking up a lot of neat things that integrate social media with email. A hat tip goes to Marius for the link.