I’m a member of the Highgate Guild, a group including some of the best-known agile software development consultants in the UK: Andy Pols, Ivan Moore, Romilly Cocking, Peter Marks, Nat Pryce, Steve Freeman, Rachel Davies .
Chris Clarke, Jason Gorman, Laurent Bossavit, Mock objects, Paolo Polce, Pascal Van Cauwenberghe, Willem van den Ende, Michael Mahemoff.
There is also a more comprehensive list of posts by category and posts by source.
The Satir systems webring brings together a number of websites related to the work of Virginia Satir and systems thinking approaches.
The systems thinking aggregator brings together blog posts from people in the systems thinking community, including my own posts on systems thinking.