MacLane is still the standard for working mathematicians, but for those with less background, Steve Awodey's book[1] is very good. He also has some YouTube lectures[2]. While you're on YouTube, the Catsters channel[3] has many excellent 10-minute category theory videos.

[1] http://www.amazon.com/Category-Theory-Oxford-Logic-Guides/dp...

[2]https://www.youtube.com/playlist?list=PLGCr8P_YncjVjwAxrifKg...

[3]https://www.youtube.com/channel/UC5Y9H2KDRHZZTWZJtlH4VbA

I can second the Catsters channel. As a complete category theory newbie watching those videos was nevertheless enjoyable because of the upbeat and cheerful attitude with which the material was covered.

I actually found MacLane's book to be more approachable than Awodey's. Although I'm not sure this is good advice because it took me several years casually feeling my way through the field to start to gain an understanding into it (ie YMMV).

Interesting category theory historical fact! Checkout MacLane's wikipedia page and you will find one of his students was in fact Steve Awodey.

> 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.

I have always sworn by Borceux' Handbook of Categorical Algebra. It progresses smoothly all the way from first principles up to (if you buy all three volumes) sheaves and topoi, but it is kind of expensive.

Thank you for the recommendation.

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

By the way, it's not two authors; the single author's name is "Saunders Mac Lane".