While there are some security considerations related to the enabling of cookies and JavaScript in order to get this extension to work, it is really a cool addition to your site.

AnyWikiDraw runs a Java applet in your wiki that allows the editing of SVG, PNG, and JPEG images directly in the wiki. For sites where kids are a primary audience, this extension can be a great addition.

http://www.mediawiki.org/wiki/Extension:AnyWikiDraw

Tooltips are a great way to teach people how to do something. For educational wikis, or wikis that attract a great deal of new users, the addition of tooltips can really give your wiki some pop.

The Balloons extension provides the magic tag<balloon> that allows you to add pop up tooltips to images and text in your wiki.

http://mckay.cshl.edu/wiki/index.php/MediaWiki_Balloon_Extension

Wikis don't have to be boring. With the CSS MenuSidebar extension you can jazz up your site a bit with some CSS. You can create additional sidebar elements as a menu with dropdown items.

Along with the extension, you will need to copy a CSS file to your server as well so you can style your menus.

http://www.mediawiki.org/wiki/Extension:CSS_MenuSidebar

Category clouds are extremely popular on blogs thanks to a simple plugin made available from WordPress. With MediaWiki, an extension called CategoryCloud creates a tag cloud for every subcategory in the category.

Each word can be resized based on the number of children, both category and articles, in each subcategory.

http://www.mediawiki.org/wiki/Extension:CategoryCloud

Wikis are all about collaboration and sharing, so why not share your Flickr images with your wiki's audience.

Using the Flickr extension has some advantages over uploading and embedding files. First, you don't have to store them on your server so resources such as storage and bandwidth aren't being used.

Second, you can keep the comments from Flickr so that they can be shared as well.

http://www.mediawiki.org/wiki/Extension:Flickr

We saw earlier in the book how to playback Flash and Ogg files with separate players. The MediaWikiPlayer encompasses many different file types and allows you to play them back over your wiki.

By adding the URL of the file between two tags,<mediaplayer arg=value > and</mediaplayer>, you can play the following file types:

http://www.mediawiki.org/wiki/Extension:MediawikiPlayer

Want to send a tweet when you wiki is updated? SendToTwitter is an extension that will do just that. You can customize your message and the extension will automatically shorten the URL for you.

http://www.mediawiki.org/wiki/Extension:SendToTwitter