Agile Manifesto – The cornerstone of agile.

Agile Mentor Circle – A peer-to-peer support group founded by Georg Fasching and David Lowe. Applications happen quarterly and the group meets (online) fortnightly. РProduced by Ken Schwaber and Jeff Sutherland after they broke away from Scrum Alliance. The Scrum Guide is an invaluable resource for the basics of Scrum. The site also has a very useful glossary.

Scrum Alliance – A not-for-profit professional membership organization that runs training courses and has an active community.

The London Agile Discussion Group – a fortnightly meetup discussing various topics around agile, Scrum, Kanban.

KanbanDev – a Yahoo forum discussing Kanban.

Lean Kanban University (LKU) – a fantastic resource to learn about Kanban.

Limited WIP Society – a global community embracing Kanban for software development.

What Mike Said – a bit of fun created during a hack day which asks a virtual Mike Cohn (from Mountain Goat Software) to give you an estimate for your stories (along with some insights into what your team is thinking).