I've been doing a lot of reading and researching about shoes lately - trying to learn as much as I can to make sure I get the right type of shoes for my feet, gait, and type of running - especially since I am starting to push my distances out past 50K. So far, I have found a few resources that have some good info, and wanted to pass these along to anyone interested.
First is The Lore of Running by Dr. Tim Noakes. The book is a brick - once you're done reading it, you can always use it in your strength training, it weighs that much. He covers all aspects of running, including physiology, ultrarunning, and, of course, shoes. It is considered THE authority on running, and Dr. Noakes is a highly regarded physician and research scientist, as well as endurance athlete. This book belongs on every runners bookshelf.
I've already written about this blog previously, but wanted to mention it again - The Science of Sport. It's a great blog by a couple of guys who got their Ph.D.'s from the University of Cape Town, where Tim Noakes teaches. They recently did a series on shoes. Click on the "Featured series" link at the top, as they recently did a series on shoes.
Here is a link to an article referenced in The Science of Sport post on running shoes: http://www.quickswood.com/my_weblog/2006/08/athletic_footwe.html I'm still reading it, but so far it seems like some good info.
And here is a link to another blog referenced by The Science of Sport: http://barefootrunningshoe.blogspot.com/ This one is geared towards the barefoot crowd. I have recently started incorporating some barefoot running into my weekly training, as from what I have read so far it can help strengthen a lot of little muscles in the feet that don't get worked much due to the support shoes give. Since I have been working out with my local track club once a week - the Santa Cruz Track Club - I decided to do the barefooting after I'm finished with the weekly workout. So far, I have done it the last two weeks for about a mile each week. Can't say I notice anything different yet, but I'm not feeling any pain.
Another great book I recently bought is titled Fixing Your Feet by John Vonhof. This one is highly regarded in the ultra community, as I had seen it referenced in lots of places and seems to be "the reference" for everything feet, including shoes.
I can also recommend another book called Running Strong & Injury Free by Janet S. Hamilton. My wife has had this one for quite some time, and I just recently picked it up to see what it was all about. She has a nice section on "Understanding the Biomechanics of Gait" that is quite helpful and includes a section on shoes as well.
I'm sure there are lots more resources out there, and I'm hoping you will chime in with any you know about. I'm always looking for good, new stuff to read so lay it on me! :-) I'll update this post periodically if I come across anything new as well.
Good luck, and happy running!