WP-MediaWiki adds a subset of MediaWiki markups to WordPress. 
Currently, the following MediaWiki markups are supported.
<ul>
<li>Bold</li>
<li>Italic</li>
<li>Heading</li>
<li>Lists: Besides the list markups come from MediaWiki, I also added a continuation markup such that users can put preformatted text in a list item.</li>
<li>Tables</li>
<li>External links</li>
<li>WikiLinks: the wikilink will link to Wikipedia by default, you can change the wiki site in the admin option page.</li>
<li>Table of content</li>
<li>Horizontal line</li>
<li>Preformatted text</li>
</ul>
For more information about MediaWiki markups, please refer to http://meta.wikimedia.org/wiki/Help:Editing. 
For a demo of this plugin, please refer to http://zechs.dyndns.org/wordpress/?page_id=152. 
There is also a sandbox (http://zechs.dyndns.org/wordpress/wp-content/files/wp-mediawiki/sandbox/index.php) for you to preview the effect of this plugin.

WP-MediaWiki

WP-MediaWiki is a plugin for WordPress. It adds a subset of MediaWiki markups to WordPress.

darrinb

Easily include raw markup languages (HTML, CSS, PHP, etc.) in posts using custom quicktags. No need to encode, the filter does it 
for you. Creates convenient “encode” buttons for post authors in the HTML editor.

WP-MediaWiki vs WP Post Encode