Fixing your feet: Prevention and Treatments for Athletes, John Vonhof
Ultramarathon Man: Confessions of an All-Night Runner, Dean Karnazes
Never Wipe Your Ass with a Squirrel, Jason Robillard
Relentless Forward Progress: A Guide to Running Ultramarathons, Bryon Powell and Eric Grossman
Total Immersion: The Revolutionary Way to Swim Better, Faster, and Easier, Terry Laughlin
The Art and Science of Low Carb Performance, Jeff S. Volek and Stephen D. Phinney
www.runnersworld.com; You can find lots of running information here. Primarily directed at road runners, but they are branching out into trail running and ultrarunning.
www.zombierunner.com; Shop here for any of those hard to find ultrarunning supplies
www.runnersconnect.com; resource for online coaching, strength training, and tons of excellent running information.
www.pearsports.com; real time coaching program
www.kemmefitness.com; strength training programs specific for runners both at the gym and at home. Includes ideas for building your own weights at home.
ultrarunningmom 
I noticed that you recommend Total Immersion. How do you fit swimming into your ultra training?
I use it as cross training, swimming and cycling both. Especially early in training, then I can exchange them to increase running as I peak for the race.