A number of teachers have told me that Rationale (which started life as Reason!Able) is an excellent tool for supporting argument mapping by providing a structure for constructing and analsysing arguments.
Debategraph takes argument mapping to the social web. It’s a creative commons wiki and its goal is to increase the transparency and rigour of public debate. Users can create and reshape debates, add new arguments, filter and rate comments, and monitor the development of debates using RSS. Like new entries on Wikipedia, new debates will be unbalanced and immature until the iterative process of collaboration and revision engages opposing views and supporting evidence.
