A fascinating search system that uses semi-structured searching of Wikipedia (in this demo - the method is generalisable) to graphically show links between two different concepts. It's quite beautiful to watch the concept map grow. A potentially very valuable tool that can provide a rich overview of a subject area using crowd-sourced knowledge to abstract a collective view of connections between topics. 

It has some notable interface issues (it appears to use Silverlight :-( ) but it's an extremely promising approach to mining for and visualising something akin to collective wisdom, with a clear focus on generating something of value to learners.

Like the vast majority of systems that look at knowledge structure as a means to organise information for learners, it is worth observing that knowledge structure is far from equivalent to the best pedagogical structure so this is not a means to establish a learning path. However, to provide a useful top-down overview of an area of interest and its connections to other things, as well as to draw attention to the crowd-perceived importance of particular aspects of an area, this is pretty cool.