The Natural Running Center has a free e-booklet on the topic of “Healthy Feet”. It’s 72 pages and full of content. From their own description:
The main attraction of the booklet is an extensive footwear study that appeared in a medical journal from 1905, and which arrived at the unvarnished conclusion that most “modern” shoes are harmful to the health and development of the human foot.
It’s worth a read. You can download it from here.