Independent Math Study
sdesol: It's been ages since my last university math class (I was a I math major), so I can't point you to any reference material, but I can say the following.If you really want to improve your problem solving skills, I would highly recommend studying real analysis.  What you get out of this will go a long way to making you a better problem solver.  The reason why I say this is when you have to so something like prove why 1 is greater than 0, you'll learn to look at things differently.In studying real analysis, you are almost learning how to walk again.  Everything that you have taken for granted as being obvious in the past will now have to be proven.  And by going through these exercises, you'll learn the importance of truly understanding what you are doing.