NationBuilder - The world's first platform for leaders, handcrafted from scratch to help you grow your community and lead them to action.
Crowded Communities - The all-in-one community platform.
Invision Community - Invision Community is a flexible, integrated set of apps for building communities on the web.
Mobilize - Mobilize is a scalable messaging app built for large groups.
FUEL CYCLE by Passenger - Think Passenger builds online platforms that allow brands to connect, create and communicate with key stakeholders.
Spot.IM - Spot.IM offers a set of tools and technology for your online community management.