Microsoft has a wiki. It is called the TechNet Wiki. It is free-as-in-beer.

A one minute “fly-through” video is at: http://youtu.be/gj5Ug0CEg70 

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One of the “wiki ninjas” (a group of wiki early adopters committed to helping others use the wiki) has compiled a nifty list of wiki articles that will help you get up and contributing on the wiki.

If you use Twitter, follow the hashtags #TNWIKI and #WIKINIJAS