We have been using (while being developed by sylvie's & other devs.' nice work) some new features in TikiWiki 1.10, highly suitable for educational scenarios (Contributions & Action logs, mainly, with some improvements to Tikisheets in our specific case of experimental sciences). These features would be quite ready for production use, if we wouldn't have to wait until 1.10 is released as "THE" stable version... (who knows when..., but each time closer as 1.9.x matures, times passes, and 1.10 seems to be pretty stable already )
The United Nations Educational Scientific and Cultural Organisation recommends and lists Tikiwiki as a Productivity Web Tool:
Tiki CMS/Groupware (aka TikiWiki) is a powerful open-source Content Management System (CMS) and Groupware that can be used to create all sorts of Web applications, Sites, Portals, Intranets and Extranets. TikiWiki also works great as a Web-based collaboration tool. TikiWiki is a multi-purpose package with a lot of native options and sections that you can enable/disable as you need them.
Interaction: TikiWiki is a content management system for writers. It supports wikiwiki web pages, blogs, CMS news article publishing, discussion forums, a directory of links, a calendar, RSS newsfeeds, user-designed databases for tracking contacts/events, and many other things as lots of people added code to the product over the last year.