Google+ isn't a ghost town anymore: populate your circles with Science! I co-curate Science on Google+: A Public Database, which among other things is a database of more than 600 different scientists, science teachers, and science writers active on Google+. We also host hangouts and provide a forum for asking science questions and finding collaborators among scientists on Google+. We also work closely with (and contribute to) two other science pages - STEM Women on Google+ and Science Sunday.
ThinkUp is a powerful, free, open source PHP/MySQL app that you install on your web server to collect and store all of your activity on social networks like Twitter, Facebook and Google+. It can analyze your activity, lets you search for your data (even past Twitter's search limits!) and is constantly being extended with new features and capabilities by a very active, diverse developer community. [more inside]