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.
An ad-hoc, location-specific messageboard. Grabs your location and creates a messageboard based on messages sent by the people around you; the more messages there are near you, the more geographically-focused your messageboard is. Hopefully useful as a backchannel for conference talks, protest demonstrations and more. Photos, files, OpenID, ActivityStreams and APIs to come.