Inquirers.Org website/blog -- by Lindsey Ferrie & Simon Davidson (one of the editors of "Taking the PYP Forward)
Inquiry Schools website -- featuring videos of Kath Murdoch and Kathy Short, etc., in action
Inquiry Teaching & Learning ning [NB: no longer working -- now that nings are no longer free]
Inquiry & Thinking Tools -- part of school library wiki of Eileen Hurley in China
From a 2009 book -- Taking the PYP Forward -- Chapter 1: Inquiry as a Stance on Curriculum -- by Kathy Short
From the book, Black Ants and Buddhists -- by Mary Cowhey
A LibraryThing booklist developed with PYP workshop leaders in mind, but good for teachers in general -- created by Ingrid Skirrow.
PYP Professional Development booklist -- created by Katie Day in GoogleBooks - books by Kath Murdoch, Kathy Short, and others