I am in the same boat as many bioinformaticians, where I got my degrees in biology and taught myself computer science, and that's gotten me pretty far. But unlike those lovely physicists-turned-bioinformaticians, I only took the required maths courses ten years ago and wish I'd payed more attention.
As far as I can tell it's currently for me more of a problem of concepts, and familiarity with symbols. For example with the latter, when I get to a part of a paper with equations, my eyes just gloss over... I'm not used to reading equations, so it's difficult for me to parse them or understand them in context- everything from 'what is that greek letter pronounced as?' to understanding the general form of the specific equation.
What is a good way to get up to speed on the important mathematics in my field? Most of the stuff I come across is either too high level (academic texts) or too low level (Khan Academy, for example). I feel that this lack of knowledge is really limiting the directions I could take my research and tools I could use, but I'm not sure how to go about improving it.