Collaborative Website System
If you're looking to create a website around a certain topic, you might be interested in NewsCloud.com. Jeff at Idealog says:
If you're looking to start up your own online media publication but want something more sophisticated than a blog, check out the latest release of the NewsCloud Open Source Media Platform. NewsCloud.com is a social network for news, like Digg but open source with a greater emphasis on building grassroots networks for collaborative journalism.