University of Cambridge (UK) http://orbit.educ.cam.ac.uk/wiki/OER_teacher_education_resources - has some OERs (open educational resources - FREE) that you might have considered for primary/elementary math and secondary/high school

I've got no idea why they don't include
http://www.oercommons.org/ or other OERs/MOOCs except that it's probably trying to simplify the situation.

I'd also suggest the book Number Devil too or Hoagie's site (http://www.hoagiesgifted.org/math.htm).