Here you will find some helpful links

For quality tack and gear:

Horse and Mule Gear

http://www.horseandmulegear.com/

King's Saddlery 

http://www.kingssaddlery.com/

Cameron Equine Products

http://www.rockymountainmules.com/

For improving your horsemanship:

Harry Whitney

http://www.harrywhitney.com/

Ross Jacobs

http://www.goodhorsemanship.com.au/index.html

Tom Moates

http://www.tommoates.com/books.php