Which publishers use TeX and derivatives (LaTeX, ConTeXt, and friends) for a significant proportion of their published books? Note that I am not asking about journals.
I'll leave the interpretation of "significant proportion" open. "Most books within a few subfields" counts; but if it's only "most math, physics, and computer science books" (which will be true in a lot of cases), please indicate so in your answer, as this will help us see which publishers try to use systems from the TeX family even in fields where (La)TeX doesn't dominate.
Note: All publishers regardless of size or fame are welcome in answers. If we need to regroup the answers into categories (such as "university presses", "large international corporation$", "publishers focusing on locale X or language Y"), we can still do that later.
Best Answer
There was a thread on this on TeXHax a while back: http://tug.org/pipermail/texhax/2007-June/008538.html
And that discussion resulted in this web page: http://www.ccrnp.ncifcrf.gov/~toms/latex.html#tex-latex_publishers
I trimmed a few out-dated entries, and did not consider the ``significant'' aspect: