DokuWiki is a standards compliant, simple to use Wiki, mainly aimed at creating documentation of any kind. It is targeted at developer teams, workgroups and small companies. It has a simple but powerful syntax which makes sure the datafiles remain readable outside the Wiki and eases the creation of structured texts. All data is stored in plain text files – no database is required.

Multi-level category system, with unlimited number of categories. Integrated search engine. Completely template-driven: change the directory appearance by modifying just the template files. Add/edit/delete/move pages and categories easily. Move full parts of the directory (subcategories and listings) with one click. Semi-automated directory: users suggest urls and you accept/reject them. IP banning.

stackoverflow clone script OSQA is an open source and easy to use social question and answer system that provides wiki-like features and a voting system. OSQA can be used as an interactive FAQ system for websites and web applications.

Qwench is a PHP/mySQL based StackOverflow clone.

This is Askbot project - open source Q&A system - askbot-devel repository is open to anyone who wants to help develop Askbot - Askbot is based on code of CNPROG

 

A Q&A site helps your online community to share knowledge. No matter what your area of interest, people with questions can get super answers fast.

An open source Q&A(question and answer) eco-system

stackoverflow-like app written in ruby, mongomapper and mongodb Question Vote script.

Features include an integrated payment system with PayPal, link validation, SEO urls, unlimited categories and subcategories, reciprocal linking, link editor, template driven system compatible with phpLD templates and many more

Php weby free link directory script is licensed under GNU GPL license.

PHPLinks is an open source project written in PHP for use with MySQL, allowing one to run an extremely efficient Link Farm with full search capabilities. A "simulated" search engine in many ways.

 

Meeplace is a Business Review CMS (Content Management System) that you can download, install, and use to create your own review site. Not only does Meeplace provide easy solution software that allows your visitors to submit their own reviews on businesses, cars, movies, or whatever content you have listed on your site, it is also a great way for your visitors to talk about their own personal experiences with companies, car dealerships, or even the local handyman. Use Meeplace to start your own business review site, product evaluation site, or directory site in minutes. You can feel secure knowing our code is not outsourced and everything is created internally by our company.

Eventicus is a social event community

Arfooo Directory is an open source software distributed free under the Creative Commons Licence.

Cahoots! is a community-building platform written in PHP, and designed for encouraging interaction and Q&A in a technically-oriented community.