As has been noted, some topics do run "across" sites. I do have a background in OR/MS myself and lo and behold so far I have been on Mathematica.SE and a bit of Stats.SE.
I have specialized on System Dynamics (SD) which is a systems modeling paradigm introduced mainly by Jay Forrester in the late 50s.
As of a week ago I have proposed a new Stack Exchange site in Area 51 which I have called Modeling and Simulation. The core criteria for that site in my opinion are:
- use of models (which includes conceptual models not only quantitative models)
- and/or use of computer simulation typically (but not exclusively) using common paradigms like System Dynamics (SD), Discrete Event Simulation (DES) or Agent-based Modeling (ABM)
- supporting decision making in management of a complex system (e.g. some link to optimal control)
It is of course all fresh but instead of running around on very specialized sites there is merit I believe to have a dedicated page for Modeling and Simulation for Decision Support. Especially since pages dedicated to OR/MS, or System Dynamics and other topics in this area are often raising too little interest.
Maybe that is a site for you (and hopefully others) to help grow?
As of today I have created a proposal for Management Science on Area 51 which I feel is somewhat lacking -- and which has an even broader focus than Modeling and Simulation.