This page builds mind-maps of wikipedia!
Start by typing something into the searchbox and clicking a start topic from the list of links.
That topic will float onscreen as a single node.
Try clicking on that node to expand it.
A linked node will show up, corresponding to a random link from that article.
Double-click a node to see the corresponding article on the wiki.
(Note: you'll probably have to "allow popups" in your browser for that to work.)