Behind their tecchie names, AddThis and ShareThis are simple services: they allow web-developers and less tech-savvy users to integrate social networking "share" buttons on their site. While they might also offer some additional services such as analytics, these tools gained traction mostly by providing an easy and free way to integrate Facebook, Twitter and other social networks share buttons. Anyone can use any of these service and in a few clicks be provided with a plugin for their site or a…