Mediawiki is free software, it is famous as the software platform used in the success of Wikimedia Foundation projects, the most widely known one is Wikipedia. The greatest success in the social construction of information in the world.
The largest and most successful free knowledge projects in the world and all this free from proprietary contraints. Most educational institutions haven’t even comes close to this success in the advancement of human knowledge, in fact the opposite is true.
Not only has it contributed to the success of Wikimedia projects but its also used in many educational projects, like Wikia, a mobile audio encyclopedia, the one laptop per child project, UNESCO International Institute for Educational Planning’s Open Educational Resources Community, wikieducator, wikischolar and many, many, many others.
Mediawiki provides a simple, feature rich environment for editing and contributing. Its ease of use has no doubt been a contributing factor in the growth of human knowledge.
I use Mediawiki for my Wiki, there’s a collection, of hacks, extensions and tools for extending Mediawiki thats constantly improving every day. You can see the details of how I set up my Wiki here.