Thanks for all the advice, I've pondered quite a bit on this.
I've decided to get Mathematics and Physics for Programmers now. It covers a lot of ground I'm already familiar with, but it really seems like a comprehensive reference of all the basics, explaining them much better than Wikipedia (which I usually turn to for refreshers). And it really covers a lot of ground, from what I've seen pointing to more advanced books for further reading. But it does seem to cover all the things I really need right now.