One of the best blogs on feet and orthotics...

http://www.podiatry-arena.com/

Just an opinion, and at  podiatry-arena, everyone has them.  It is dominated by persons with lots of experience and seemingly lots of time on their hands to write responses.  These men and women are devoted to the theories and techniques of foot and ankle biomechanics and, although the discussions are highly technical, you'll find an answer to virtually any podiatric question you may have.  Go and Play!