There's a first demo impl of InstantCommons up at: http://141.13.22.239/ic-client/index.php/Main_Page
What this does: Allows any MediaWiki installation to transparently load (and cache) images from a central repository like Commons, provided the repository permits it. Ideally, Wikimedia Commons will do so, and any installation in the world will be able to use files from Commons as if they were locally uploaded.
The current code is in the instantcommons branch. There are still a few issues and it's not feature-complete yet before it can go to the official review.
mediawiki-l@lists.wikimedia.org