While this book is a little outdated, it is still a good resource for when you're on the road. It provides a list of health food stores and vegetarian restaurants. I really (really) wish the author would update it, so much has been added (and subtracted) in the last 9 years.

Sadly it is pretty outdated but is still somewhat useful. You just need to call ahead and verify the places are still around. I really wish there was a new edition available.