For me, it's definitely Ribbonfarm:http://www.ribbonfarm.com/
I stumbled into Venkat's blog about two and half years ago and I'm still trying to find my way out. The rabbit hole gets even deeper when you look at his list of recommended reading. The material on John Boyd and OODA loops in particular has been bouncing around my head for about a year. Ribbonfarm quickly turns into a choose-your-own-adventure type of experience as it's very easy to bounce between articles and start looking everything that you don't know.
If you're interested in getting below the surface level of how organizations, teams, and business cultures work Ribbonfarm is the best place I know of that really digs into the details. If you're expecting the typical "be a leader, not a manager" platitudes, then you'll be disappointed.