I personally do like the IkeWiki approach based on Mediawiki. The paper A Semantic Wiki for collaborative knowledge formation (pdf) summarizes nicely knowledge models, while the paper IkeWiki: A Semantic Wiki for Collaborative Knowledge Management (pdf) explains the actual IkeWiki itself.
MediaWiki can become a de facto standard as its learning curve can be painless:
editing Wikipedia -> own MediaWiki -> Mediawiki w/ integrated WP -> IkeWiki
(Worth noting again that the only knowledge management application I know that actually works is System One.)