http://www.amazon.com/Engineering-Mathematics-K-Stroud/dp/1352010275
This is the book I've mainly been using to upgrade my math. HIGHLY RECOMMENDED for self study! I like it because it is a "programmed text" where there are usually four or five small bits of information and a problem or three, per page. So, it is light on long exposition and able be to digested in small bites. My calculus is better now than it was after 2nd semester in college. But not good enough, yet. I also have the follow on "Advanced Engineering Mathematics", which I am using for an overview of Linear Algebra.
But something much more pragmatic might be more motivating. So, I may attempt Coursera four part "circuits" specialty. I'm almost through build-out and rent up of my first 5 apartments. If I can get tenants in within the next month I ought to have more energy and time to turn back to exercise, math/physics, and maybe a little fun!