Book recommendations for relearning math from elementary school arithmetic?

The first thing you need to do is to figure out how much you know. You need to know which level you are at.

I recommend going to someplace like khanacademy and try some of the exercises.

Another thing I like to do is to find something that I want to learn, that at the moment is over my head. Then I figure out, what do I need to know to understand this? Then I can make a list for myself of concepts/techniques I need to learn.

There are lots of good books about math. Here's one such list:

http://www.amazon.com/Books-about-Math-Numbers-More/lm/R3T29ZJGFBT60N

These tend to be more about the ideas in math than the techniques of mathematics, but they might be good motivation. Personally, I liked "Shape of Space" (number of 24 on the list) which helped fill some holes in my background on topology, and also "Fooled by Randomness" (number of 21 on the list) which gives an accessible intro to the ideas of probability.

I am sure you will get many useful tips for material, however I have one suggestion. Math deals first and foremost with abstract ideas that often have very simple definitions. People that are not experienced in math may sometimes confuse the fact that something is easy to define with it being easy to understand. However, one of the interesting things in math is that something can be very easy to define or write down but challenging to understand deeply and intuitively.

In my experience, one of the most important things you need to do in order to really understand math is to get your hands dirty. That means solving, calculating, proving and playing around to see what happens. This takes time and discipline, but that is the only way to go.

Good luck!