There are lots of books on category theory, and what counts for “applied” will differ depending on your background, perspective, and intended applications. This free Seven Sketches book looks promising, especially with the opportunity to join John Baez’s study group. But if you don’t mind paying for books or studying them yourself, I can recommend these as being accessible to those without a lot of college math background:
Category Theory for the Sciences by Spivak (one of the authors of the free book advertised here)
Conceptual Mathematics: A First Introduction To Categories by Lawvere and Schanuel
There are lots of books on category theory, and what counts for “applied” will differ depending on your background, perspective, and intended applications. This free Seven Sketches book looks promising, especially with the opportunity to join John Baez’s study group. But if you don’t mind paying for books or studying them yourself, I can recommend these as being accessible to those without a lot of college math background: