You could try a text like the UC Davis Book of Horses (A Complete Medical Reference Guide for Horses and Foals).
In terms of schedules for worming and vaccinating and such...the best you can do is educate yourself on the types of worms/diseases etc...and then base your decisions about schedules on what you think would best suit your horses, for the area you live, and the plans you have for that horse. Your local vet should also have input on this, though you will find vets that are at both ends of the scale, and everywhere in between, about how much and what kind.
For shoeing, you should discuss that with your farrier and hopefully you'll get a good one. There are a number of farriers who've written books, like Peter Ramey that you could peruse. You can of course visit farrier bulletin boards online and research articles online.
Supplementation I will point you to a nutritionist. Many feedmills employ a nutritionist. You can also contact a nutritionist from the feed company...know of course that they will be flogging their product. But you can at least get a nutrient breakdown of their various foods. You can also get your hay tested, which will tell you if it's rich or lacking in something specific.
There are two kinds of supplementation...daily and therapeutic. Daily supplementation means supplementing for nutrients that are lacking on a daily basis..if the hay is poor quality for instance and lacks calcium.
Therapeutic supplementation is supplementing for prevention of diseases (like arthritis), supplementing to promote healing (if the horse has an injury), or supplementing to slow the progression of an existing problem (COPD, digestive issues). These things require more than the daily amount of nutrients.
Last edited by Mercedes; 03-16-2010 at 05:24 PM.