Books/lecture notes/videos on category theory for programmer

I asked the same question about a week ago at the chat and someone pointed me to a book called The Joy of Cats. It's free so you should definitely take a look at it. I think its kind of hard but you don't lose anything by trying it.

Read "Category Theory" by Steve Awodey. It is a rigorous introduction to category theory (goes as far as adjoints, some monads, Yoneda, ... ) which intentionally does NOT include examples that only a maths major can understand. Instead, its examples are drawn from logic, lambda calculus, etc.

Another possible choice may be

Michael Barr, Charles Wells: Category Theory for Computing Science

A description is here: http://www.cwru.edu/artsci/math/wells/pub/ctcs.html

EDIT: Now the authors have kindly made a pdf version of their book available.

The link is: ftp://ftp.math.mcgill.ca/barr/pdffiles/ctcs.pdf