TWiki
TWiki is a flexible, powerful, and simple Web-based collaboration platform. You can use TWiki to run a project development space, a document management system, a knowledge base, an issue tracking system or any other groupware application. It looks and feels like a normal Intranet or Internet Web site. In addition, there is an Edit link on every page to change or create content by using just a Web browser. Features include automatic link generation, full text search, authorization based on groups, web form handling, email notification of changes, SSI, file attachments to Web pages, revision control of pages and attachments, a modular templating system with skins and more. The Plugins API can be used to build new groupware applications. Existing Plugins are spreadsheet, calendar, TOC, and more.