Rise of the wikicrats
roughtype.com
roughtype.com
If users were given trust values (think eBay feedback, but a bit smarter) and then users could in turn rate articles, that would at least partially solve some of Wikipedia's biggest criticisms (the content is unchecked and liable to spam / abuse).
Trust networks like that scale exponentially with the number of nodes (users and articles) so I suppose it would significantly increase the resources required to host something like Wikipedia.
My #1 suggestion: if you must have an "off-topic" forum, make sure it's clear that it's not the "no rules" forum.
http://en.citizendium.org/wiki/Main_Page
The basic idea is to establish experts that review articles and guarantee the quality of the articles in their domain. Seems like an interesting idea.