I have read very interesting list of Knowledge visualization tools. Read both the post and comments. They can be used when you carry on research.
An excerpt from the blog
Most traditional personal knowledge management (PKM) or personal information management (PIM) applications offer the same basic set of features:
* Storage of notes and documents
* Search functionality and keyword/tagging capability
* Outline view in a traditional hierarchy, or user-defined views
* Task management, calendar, and contact management (mainly PIM, not KM)
These are essential features, however don’t offer too much to the more visually-inclined knowledge junkies. For visual learners and information visualization fans, having a graphical representation of knowledge and seeing how things relate is a must have feature. Luckily, in the past few years there has been a rise in the number of knowledge management applications that offer this capability. The following is a list of interesting /unique / effective tools for knowledge management and information visualization (not listed in any particular order):