MediaWiki 1.5
MediaWiki 1.5, the next version of MediaWiki, is planned to be released soon (the announced date was 1 June 2005).
It is operational on the test wiki http://test.leuksman.com/ , where also an overview of the new features can be found.
Although MediaWiki 1.5 is currently in a beta stage, all WikiMedia wiki have been upgraded to 1.5. Third-party users should probably not use this beta release to run a public site unless paying close attention to development and ongoing releases.