wikispaces, a long running, but very powerful wiki tool that's cheap, fairly pretty as wikis go, and dirt simple to use. Just to recap, a wiki is a website where everyone involved can read, write, edit and comment on pages in the site. It's a website with no webmaster or mistress, no central command and control and no predetermined hierarchy. While that may sound like a recipe for anachy, in fact, in the wonder, organic magic that is the social web, it results in an emergent behaviour that tends more to order than entropy. Wikispaces, at wikispaces.com is just one of dozens of wiki products out there. Another one, ProjectForum, from here in canada, is another fave of mine. You can be up and running on wikispaces for free and in minutes. Wikispaces has a great What you see is what you get page editing interface, allows you to customize the look and feel of your wiki site and can maintain a history of changes and discussions for each and every page. The free version features Google ads on the right side, but they're not intrusive. You can upgrade to get rid of the ads and to add even more customization to your site. And, if you're a nonprofit and a member of the organization techsoup, you can get wikispaces for next to nothing.
Links:
[1] http://rabble.ca/taxonomy/term/144
[2] http://rabble.ca/taxonomy/term/1921
[3] http://rabble.ca/audio/by/artist/wayne_macphail
[4] http://rabble.ca/audio/by/title/episode_six_-_wikispaces
[5] http://rabble.ca/audio/by/album/online_tools_for_the_21st_century
[6] http://rabble.ca/audio/by/genre/podcast
[7] http://rabble.ca/audio/by/year/2007
[8] http://rabble.ca/user
[9] http://rabble.ca/user/register