The Meetup Python SDK by Meetup and author Doug Tangren allows API interaction to access community features that can be integrated into social media applications. Authentication, Key, requests, and responses available at https://github.com/meetup/python-api-client/blob/master/oauth.py
Think signing petitions is useless? There's probably an app for that. But Change.org proves the cynics wrong--every day. And now there's a Change.org API to rattle the powerful even further. The API is in beta, is free, and uses REST with JSON returned. The API covers a multitude of requests from creating petitions to checking signatures, from looking at the case for a petition to updating them.