PyLucid is a Open Source web content management system written in Python using the Django Framework. fully customizable output, expandable with plugins, i18n, L10n, Revision controled, support many database engines, WSGI conform and many more...
The Floranta libraries provide components for building Rich Client Wikis using AJAX or Java. Floranta clients can be embedded in any webpage (even plain html) and allow users to leave notes, images, cards, etc on the pages. Eg: http://www.floranta.com
xaos is a wiki-like hypertext system featuring RC suppport and some other goodies. Try it - its still beta.. I am also looking for people who would like to
help.