I am in my early thirties and honestly, I cant claim to have a good background in math.
But, I now have a burning desire to learn it from the ground-up.
What are the 'canonical' sources for math, both online and offline? I am lost as to where I should start. I want to have a fundamental, intuitive understanding of it.
To clarify, I would not consider it shameful to start at whatever level necessary (even the lowest, if required).
www.betterexplained.com has some good tidbits for math.
I've found MIT's opencourseware to be a pretty good help: http://ocw.mit.edu/OcwWeb/web/courses/courses/index.htm#Math...
Only the undergraduate courses tend to have video lectures though. The ones on linear algebra and diff eq are quite good. When I first learned matricies in high school, the teachers just went through the mechanics of how to manipulate them and how to calculate a determinant. It wasn't until years later, and when I started wtching these lectures that it crystallized for me what it actually meant.
These are monthly lectures on math topics, which have been enlightening. http://www.ams.org/featurecolumn/index.html
If you like exploring, there's this: http://www.jimloy.com/math/math.htm
some free online texts http://www.math.gatech.edu/~cain/textbooks/onlinebooks.html
If you haven't had a course before, you can just follow the usual sequence of courses that high school students and college students take. calculus, multi-var calc, diff-eq, linear algebra, probabilty. And get a textbook and work through the problems. If you code, discrete math will probably help somewhere along the way. Probability/stat for machine learning.
If you've already had the stuff before, It might help just to pick one small topic in a math field, like gradients in multi-var calc, and just focus on that for a bit, and inevitably, it'll mention some other math tool that you don't know about, and just follow your nose and interests.
What I didn't learn until after I finished undergrad is that if you want to really understand conceptually what things mean in math, and not just how to manipulate symbols, there's no getting around working on problems paper (or matlab/mathematica) and just playing with it.
Hope that helps.