I've been exploring several MediaWiki-based resources lately and am trying to help the Christian community consolidate information so we're not doing a lot of redundant work with resources. I keep shifting from one Christian wiki site to another, mainly in an effort to glean the best aspects of each site and discuss how we can centralize the content more effectively. It's also been fun meeting Christians with different beliefs and visions for the wiki community. I generally try to focus on contributing to Wikipedia, but some topics are considered too specialized (like articles for every verse in the Bible), which is why I've ventured out looking for Christian wikis.
There are two or three other Christian wiki users looking to collaborate across different MediaWiki sites. As of August 2006, we haven't made much progress on creating a central discussion and collaboration website, but I've got high hopes that we can make one! The best we've done is a discussion on WikiChristian. It seems to be theological opinions that divide us on the content-focus of each Christian wiki; while that is fine, I think it would be worthwhile to share the resources and information that we do have in common and point to the wikis that have been the most technologically innovative on certain topics.
I'm starting to ramble, but I wanted specifically to recommend the Bible wiki sites Wikible.org (Protestant slant) and BibleWiki (Wikipedia-like NPOV) as they've done a good job focusing on a particular Christian topic (i.e. Holy Scripture). See particularly Christian wikis and Bible wikis comparison on Wikible. I'm aware of the Other wikis page here, but the Wikible page is much more up-to date and comprehensive.
The Orthodox perspective, in particular, is one that our collaborative efforts are lacking. Please add a new section to my talk page if you would like to discuss inter-Christian-wiki collaboration (my talk page isn't limited to collaboration discussion only, of course; use my "E-mail this user" link if you like, as well)...