If you didn't see the Chrome extension, it's worth a try - I really like the feeling of serendipity every time I create a new tab. It's a little distracting, but I think in a good way.
I had a similar prototype idea that I never built, but it was this:
* start a user off on a random wiki page.
* Don't encourage them to start afresh .. they can instead click through to a different page from the current one.
* Keep track of these traversals, and then allow the 'trail' to be shared with others.
It could be cool to see the wiki-trails people leave as they spend time soaking in the pages. Or compare trails of people from the same page.
You have some of it ready.. please steal this idea :)
I thought this sounded familiar, and I managed to find this app[1] that claims to feature a "2D mind map to keep track of your journey and suggest new paths".
I dig it, but the main content area is too narrow.
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Edit: My previous endorsement is now retracted, installing the Chrome extension changes the default new tab behavior. Hijacking default browser behavior is terrible. Bad form on the part of the author
TheWikiGame[0] is my favourite go to Wikipedia based game. Mostly because a non-automated version can be played even on the most restricted networks that just allow Wikipedia.
I have endless fun working out how to get from Norse Mythology to Arithmetic Logic Unit.