[saretired]

It obviously depends on background and goals. People who come to programming with only HS math would probably benefit most from studying (not just reading) an introductory discrete math text such as Biggs or Rosen. For calculus, linear algebra and so on one could look at MIT Opencourseware. For most people, actually learning the material requires a significant time investment, and one of the hardest things to fake is a knowledge of math.