3D Hubs - Airbnb for 3D printing
Google Groups - Google Groups allows you to create and participate in online forums and email-based groups with a rich experience for community conversations.
Muglaunch.com - Design and sell print on demand products easily @ Muglaunch
DownToMeet - DownToMeet is a platform to organize, find, and attend group events.
Zazzy - Design and sell your own 3D printed jewelry
Mighty Networks - Mighty Networks enables entrepreneurs, organizations, and companies to create and grow a community-powered brand.