Open-source toolkit for building scalable community-oriented web applications. Features a large database model of web collaboration, and over 70 application building blocks. (Linux or BSD, Aolserver, Oracle or PostgreSQL)
Free website monitoring service based on retrieving a short text file. E-mail and/or pager notification. With an overall list of monitored sites and their status.
An open-source version of the ArsDigita Community System, comprised of a Web server plus PostgreSQL database. Free download, documentation, FAQ, forums, links to existing sites using this solution. [Unix, source]