It depends on the types of programming, math, etc. For example, if you can explain a math concept through an application to a video game, then maybe Gamedev.net and Gamasutra would be good places. If it's an implementation or solution to a particular programming problem, then post it pn a blog and cite it in a StackOverflow answer if there's a relevant question out there (though you may want to find the question first in this case before writing the post).