DebateGraph is an award-winning Cloud-based collaboration knowledge cartography tool. It is in use in over 100 countries, has eleven different presentation/edit modes and the interface is available in seven languages. As of this writing (July 2013) there are over 11,000 maps at DebateGraph.
Christiane Amanpour introduces Debategraph
on "Amanpour CNN" in 2010
Major project partners include the White House, the UK Prime Minister's Office, the UK Foreign Office and CNN.
The system is free to use.