I've used TWiki for over a decade, both personally and professionally.  I've installed and used dozens of other CMS tools as well - Joomla, Drupal, other wiki tools - but I keep coming back to TWiki.

TWiki implements a "structured wiki".  In fact, the primary contributor to TWiki, Peter Thoeny, invented the structured wiki, back when most wikis were just a pile of pages.

Since TWiki is a web publishing technology, many people have written about it already, using TWiki itself.  Virtually all of the TWiki documentation is inside TWiki as well.

So, rather than listing here the various cool features of TWiki, I'll instead point you to what I consider to be the best place to go to learn about TWiki -  http://twiki.org/

Feel free to contact me if you have questions or comments about TWiki.

Kind Regards,

-Paul Reiber

http://reiber.org

TWiki has fallen behind most web2.0 developments in the recent two years, especially after it lost all of its community 2008 when it was forked into Foswiki. If you are still running a TWiki site, then consider upgrading to Foswiki as it is backwards compatible to TWiki. This decision has been made by most major TWiki customers up to now that still want an Enterprise Open Source wiki and are in need to prolong their knowledge assets.