The most intellectually stimulating website you ever encount

What is/are the most intellectually stimulating website/s you ever encountered?

The more sites you can post, the better.


They may just have a ton of creative ideas and novel theories like this one...

http://hedweb.com/hedab.htm

or this one...

http://www.rawilson.com/chaos.html

A place to figure out, how do they do that type questions like this one...

http://skepdic.com/

A great source of information on a variety of topics like this one...

http://en.wikipedia.org/wiki/Main_Page

or this one...

http://www.sparknotes.com/philosophy/index.html

A great source of information on one particulary complex subjects like this one..

http://www.iep.utm.edu/j/

or psuedo science topics like these...

http://www.4rie.com/Physics.html#anchor517134 , http://xxx.lanl.gov/PS_cache/quant-ph/pdf/0209/0209123.pdf

Or they may just be a great forum (or a particular thread on a great forum) for people to discuss their beliefs on, like this one...

http://www.able2know.com


In short, they can concern any topic, be of any variety, just as long as they stimulated you.... intellectually.

Edit: Be sure to edit your posts to reflect any new websites you remember or encounter.