By Kareem Carr
I started answering this question from a commentor,
Could you post a list of all such “Stack overflow” websites that you know… It will be helpful…
In the middle of answering, I realized that I should probably turn this answer into a post.
There are new Stack-Overflow-type websites emerging all the time. There is a site which shows many of the ones in development called Area 51.
For instance, I see a theoretical computer science one is going to go live in a few hours. I suspect that will be of interest to some readers here. A lot of ones that I mentioned recently have not existed for very long.
There is a list of established sites.
In addition, there is a very large list of websites which seem to have been created using the stack exchange software that can be found here.
I am sorry for providing so many lists but I don’t know of anywhere that has them all in one place.
UPDATE: The theoretical computer science site is now active.