The original http://stackoverflow.com/ is aimed to questions with a single canonical answer, ideally.
The questions in http://programmers.stackexchange.com/ are a little more free and IIRC it allows “opinion” questions.
Also, “Software Recommendation” is in private beta: http://area51.stackexchange.com/proposals/60887/software-rec...
For example, there are two sites for Math, one for normal questions and one for research level questions.
You can try to create your own, filling a proposal in http://area51.stackexchange.com/ .
The important thing is what type of questions you consider that are fun and useful and are not allowed now in S.O. Can you make a list of 5 good examples?