http://www.everything2.com
As devoted to trivia and facts as the SDMB is. Massive user inputted neural net of ideas.
I have joined up as Kyberneticist and have added a few new nodes on the subjects like Pseudoprimes and Public Key Cryptography.
Yes, I know, soooo exciting. 
But there is a lot of really cool stuff on there. If you guys haven’t seen it before, check it out! Try the Random Node, browse around a bit… get hooked.
My god that site is incredible! Thanks to you my productivity just hit an all time low. Good link!
Thanks. 
If my productivity is going to go down, the least I can do in the zero sum game of life is reduce that of others, right? 
One neat thing about it is that it is incredibly easy to link to other parts of the neural net. Just throw around the part of your sentence you want to link to some other concept. If it doesn’t exist yet, the link will still appear and someone may fill it in later…
I love these neural net conglomeration of facts type things.
There is an “AI” project at http://www.mindpixel.com which works on a similar premise, only with a bit more rigor and the intent of creating an AI in a similar fashion to Cyc.