There are many flavours of collaborative (or "community") websites - some using freely available software. Perhaps the best known are slashdot and plastic . Another good example is the (oddly-named) kuro5hin, which uses Scoop. The Scoop blurb says it is:
a "collaborative media application". It falls somewhere between a content management system, a web bulletin board system, and a weblog. Scoop is designed to enable your website to become a community. It empowers your visitors to be the producers of the site, contributing news and discussion, and making sure that the signal remains high.
The interface is quite intuitive and allows for submission of articles, comments, ratings etc. - and it's free. The rating system appears to work well - allowing the best contributions to float to the top. The scoop sites I visited all seemed to be heavily used, with many articles and many comments and ratings on each article.
In a report on the top 10 trends for online communities, Jim Cashel (2004) lists the following overlapping types of online communities:
Webrings
Webrings could be considered a form of distributed web community. A webring is a collection of independent websites on a similar theme, linked together by standard navigation aids which allow visitors to easily jump from site to site. A webring is usually controlled by a ringmaster who decides whether to admit new applicants to the ring. The initial popularity of webrings appear to have worn off, possibly because they tend to form closed communities, unlike the more dynamic communities that emerge among blogs linked to each other via RSS syndication. There are nevertheless still many thousands of webrings and they may re-emerge as a popular form of personal and collaborative publishing.