Spent some time trying to figure out the key features of two knowledge-organization tools, Compendium and Nestor. Here is a an initial report on them..

Compendium

http://compendium.open.ac.uk/institute/
Compendium has a database in the background so all the searches are faster and more efficient, plus it is strongly based on argumentation theory. That means that you can easily map different positions in relation to their role in an argumentation, and then use this structure to retrieve things like “who supports/opposes what”

Nestor

http://www.gate.cnrs.fr/~zeiliger/nestor.htm
Nestor instead links browser information into a concept map. It lets u re-organize web-material very efficiently, export in html, annotate portions of the material. Seems very well suited for doing online research.

A lot of useful information on such topics can be found on the ‘Knowledge Cartography‘ book.