Moodle 2.0 Wiki
Moodle currently (pre-2.0) uses ewiki as its wiki system. The Moodle core developers have decided that the code is too complex and buggy and have decided to replace it.
There are two alternative wiki systems that have the potential to replace ewiki. The first, NWiki, was created by a team in Barcelona. The second, OU wiki, was created by Sam Marshall at the Open University UK.
The Moodle community discussed which wiki replacement would work the best in this thread. Ultimately, they came to the conclusion that NWiki is the best solution. A factor that seemed to contribute greatly to this decision is that NWiki has the ability to migrate old wikis created with the ewiki system, whereas OU wiki has no migration feature.
The general consensus seems to be that OU wiki is a lightweight system, with a straightforward code-base. It uses HTML rather than a wiki-specific markup language, and mostly relies on users using the WYSIWYG editor. On the other hand, NWiki has more features, along with a more disjointed code base (most likely the result of many different people working on it). It uses the same wiki-markup that MediaWiki (Wikipedia’s platform) uses.
The Future
The Moodle developers have decided to use NWiki as the core wiki system in the 2.0 release of Moodle. However, they will be developing this wiki system quite a bit before Moodle 2.0 is released. Here is a table that compares the features of ewiki, the not yet completed Moodle 2.0 wiki based on NWiki, and the OU wiki.