Found in 2 comments on Hacker News
tel · 2015-01-04 · Original thread
If I remember correctly, Awodey[0] has exercises like that.

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

nbouscal · 2014-12-11 · Original thread
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

Fresh book recommendations delivered straight to your inbox every Thursday.