Mike Griffiths is a co-founder (with about a dozen others including me) of the Agile Project Leadership Network (APLN) who started a blog a few months ago focused on agile leadership. 

http://leadinganswers.typepad.com/

He summarizes excellent ideas and concepts in short entries with great illustrations. For instance, check out the two drawings in the entry titled Agile Methods as a Replacement for Fossil Fuels. Very, uh, illustrative!

What I've always loved about agile methods, principles, and approaches is the inherent humanity. You know, most approaches to increasing humanity, i.e., humanness, to an organization are threats to productivity and performance. And most approaches to increasing productivity and performance are threats to humanity. I've spent my career as an applied organization and leadership scientist looking for the congruence of productivity and humanity, and that congruence flourishes in the agile mindset and principles.

And Mike Griffiths communicates that extremely well.