I frequently try out and contribute to a variety of open-source online community-type tools including Mambo, Tiki-wiki, Drupal (a commercial version of Drupal = Acquia ), and Moodle. I have several currently installed and use some of them for testing out comparative features.

Several guides on the Web provide discussions of the various tools available. Wikipedia provides one of my favorite general lists here.

Web 2.0 = power. [For those unlcear on Web 2.0, here is a seminar article.] We see a trend in leveraging the parallel processing capacity of individuals through distributed information management in Wikis and other forms where people can vote and Sites can now dynamically update themselves.