> To actually learn it, Mac Lane & Saunders "Categories for the Working Mathematician." seems to enjoy continued popularity.

This is the best way I've found so far, and I had been semi-supplementing with MacLane and Birkhoff's "Algebra", just to get a feeling for the vocabulary; bringing myself from the space I typically mathematically exist in, to the space of category theory. Nothing else really has come close in composing the correct thought direction. It is dense, but I enjoy it very much. It is very beautiful math.