Agile Learning Center
Helpful Agile Links
Roman Pichler's Product Management Tools
Roman Pichler is an authority on the Product Management side of Agile. This is a link to his free toolkit.
Ken Schwaber, one of the co-authors of the Scrum Guide started Scrum.org in 2010 after breaking from the Scrum Alliance. The Scrum.org certification program has since gained traction.
Scrum Guide Download Page
Download the Scrum Guide, written and updated by Jeff Sutherland and Ken Schwaber.