Category theory formalizes mathematical structure and its concepts in terms of a labeled directed graph called a category, whose nodes are called objects, and whose labelled directed edges are called arrows (or morphisms). A category has two basic properties: the ability to compose the arrows associatively and the existence of an identity arrow for each object. The language of category theory has been used to formalize concepts of other high-level abstractions such as sets, rings, and groups.

Ologs

,
On knowledge representation through ontology logs and how it's related to category theory.

Categories: ten seconds info

The essence of category theory in plain language.

Categorical cryptography

,
An attempt to combine cryptography and category theory.
Category Theory on board.

Monads (with snippets in R and Swift)

The literature and information around monads and categories is sometimes confusing because it has many aspects and depending on the background many overlapping or equivalent terms are used.
Heavenly Spheres

A kaleidoscope from F# and monads

How categories pervades our thinking and programming.