StackExchange™—The Stack Overflow Knowledge Exchange Platform: Spolsky and Atwood have productized the Stack Overflow platform, so you can buy it as a service and customize it as a knowledge sharing site for anything.
The idea of a knowledge exchange, running the same software as Stack Overflow, can be applied to just about any subject matter. With StackExchange™, you can run a site with all the same features that made Stack Overflow successful.
Prices start at $129 a month.
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StackExchanged worked great for us for awhile. However the pricing is still a bit too high each month. We tried out Coordino and it works pretty good. It needed some customization but overall it worked as a good alternative to StackExchange. SE has better admin controls though.