Wikipedia must surely be on of the greatest innovations on the internet since the advent of Google and YouTube in my opinion.
The secret of it's success was to harness the power of user general knowledge via an extremely easy to use and read interface - a wiki. MediaWiki is a small package which contains everything you need to create your own wiki on any subject you choose. MediaWiki is already being used by several other projects of the non-profit Wikimedia Foundation including the MediaWiki developer site.
MediaWiki is basically a free server-based software which is licensed under the GNU General Public License (GPL). If you're intent on creating a big or popular wiki don't worry - it's designed to be run on a large server farm for a website that gets millions of hits per day. MediaWiki uses PHP to process and display data stored in its MySQL database. However, it requires no SQL database knowledge on your part and pages use MediaWiki's wikitext format, so that users without knowledge of XHTML or CSS can edit them easily.
MediaWiki contains everything you need to get up and running with your own no matter how big or small your project.
- Watchlists now have RSS/Atom feeds. RSS feeds generally are now hidden, since Atom is a better protocol and is supported by virtually all clients.
- It's now possible to block users from sending email via Special:Emailuser.
- The maintenance script system was overhauled. Most maintenance scripts now have a useful help page when you run them with --help.
- AdminSettings.php is no longer required in order to run maintenance scripts. You can just set $wgDBadminuser and $wgDBadminpassword in your LocalSettings.php instead.
- The preferences system was overhauled. Preferences are stored in a more compact format. Changes to site default preferences will automatically affect all users who have not chosen a different preference.
- Support for SQLite was improved. Some broken features were fixed, and it now has an efficient full-text search.
- The user groups ACL system was improved by allowing rights to be revoked, instead of just granted.
- A new localisation caching system was introduced, which will make MediaWiki faster for almost everyone, especially when lots of extensions are enabled.