We have four MediaWikis installed/integrated with National Geographic's corporate intranet:
1) LIS Wiki: We are using our main wiki -- Libraries & Information Services Wiki -- is being used for multiple solutions: dictionary/encylopedia functions like acronym list and records classification descriptinos; team sites; project management/status reports; Libraries staffs' resumes; quick reference guides; educational content; and fun stuff like favorite books and movies. We are testing out for our research guides as well.
2) Women Explorers Wiki: A wiki of over 200 women explorers with bibliographic information for our internal researchers.
3) National Geographic Magazine Wiki: Project collaboration on special issues for an NGM team.
4) National Geographic Channel International Standards & Practices Wiki: A wiki being used in three ways -- to share production standards catalog to external producers/production groups; for international staff that need information about other offices; and for internal staff.
I've integrated several extensions that people really like: RSS, Calendar, and Input Box. Currently using MediaWiki 1.8.2.
I've also installed a wiki for my professional association that you could see but it's in the early stages (www.slakm.org).
I gave numerous presentations last year: Special Libraries Association annual conference, University of Maryland and Catholic University library programs, DTIC @ Fort Belvoir (VA), World Bank, National Gallery of Art, etc.
This year, I'm already lined up to speak at the following places/venues: International Monetary Fund (February), National Institutes of Health for a Wiki Fair, Computers in Libraries (March), Catholic University (for a Library Technology class), Public Library in Arlington (VA), Special Libraries Association annual conference (teaching a class on wikis as well as speaking about building communities which will include wikis), etc.
Hope this helps. Karen