Jon Terry, COO of LeanKit put together this presentation on Kanban - An Evolutionary Approach to Agile.

From http://leankit.com/blog/wp-content/uploads/2014/02/Designing-Your-Kanban-Board-to-Map-Your-Process-PDF.pdf

A high level introduction to how Lean and Agile fit together and how Kanban and Scrum should be viewed as complementary ideas, rather than competitive approaches

Why Limit WIP? -Why it's important -Why it's hard -What you can do about it