My role model for Social Innovation is a website called Inhabitat
It's not technically a site like this where people can share ideas; more a place where sustainability and technology news related to Climate Change is reported. However, they do have a Q&A session where people can ask questions, comments where the topics can be discussed and sometimes live, video interviews.
At time of writing this, I still haven't heard a reply from them, but will edit the post if I receive one. I've been using the site for more than a year and it's been a big help in keeping track of where technology is going for renewable energy, transportation, sustainable living and more. I would recommend fellow inventors who are serious about making the world better go check it out!