Kialo - Kialo is the platform for rational debate. Empowering reason through friendly and open discussions.
Socratrees - Socratrees outlines arguments into intuitive hierarchies of supporting and opposing statements. This design is loosely based on argumentation theory. However, we do not expect you to be familiar with theory in order to start using Socratrees.
OmniDebate - A crowdsourcing and debate platform for climate change activists.
MindMeister - Create, share and collaboratively work on mind maps with MindMeister, the leading online mind mapping software. Includes apps for iPhone, iPad and Android.
DebateArt.com - DebateArt is a unique and growing community committed to the idea of exchanging views and perspectives through debating.
Discourse - Discourse is an open source discussion platform built for the next decade of the Internet.