Rapportive, a small company that offers a free, enhanced contact information add-on for Gmail has just been snapped up by "professional" social network LinkedIn. If you're not familiar with Rapportive for Gmail, it's quite a bit like the popular Xobni for Outlook: it adds a sidebar to your Gmail interface in Chrome, Safari, or Firefox and attractively displays contact information with the added benefit of social network integration — your contact's Twitter, Facebook, LinkedIn, and Skype information is all built-in and viewable at a glance. While neither Rapportive nor LinkedIn have yet revealed what's in store, the former promises that it'll continue to support the popular add-on while working on its next project — whatever it may be.