Some useful links:

Action Company
Agway Products
AlphaSonic
Amerdon International
American Association for Horsemanship Safety
American Holistic Veterinary Medical Association
American Horse Council
American Horse Network
American Miniature Horse Association
American Quarter Horse Association
American Veterinary Chiropractic Association
American Veterinary Medical Association
Animal Legends
Animal Poison Control Center
Ansur Products
Apaloosa Horse Club
Arbico
Arena Clear
Argus Development
ASPCA
Assurance Feed
Auburn Labs
Behlen Manufacturing
Beneficial Insectary
B.E.T. Laboratories
Best Friend Equine Supply
Bevav Saddlery
Big Top Manufacturing
Biomedica Labs
BMB Tack
Bob Mickler's Lifestyle & Performance Riding Apparel
Books on Horses
Brower Products
B&S Horse Management Software
Bubba's Molasses Kisses
Bucas of Ireland
Buckeye Nutrition
Bufftech
BuildWorks
BuySelect.com
BYD Software
Canadian Arabian Horse
Cashel Company
Centaur Fencing Systems
Charles Owen & Co.
Chaskit Horsewear
Classic Cover-Ups
Corona Products
Courbette Saddlery Co.
Cover-All Building Systems, Inc.
Cowboy Tack
C&W Western Horse
Davis Manufacturing
Donalex Corp.
Dover Saddlery
Dr. Benson's
Dust Pro, Inc
EasyCare Inc.
Eleanor Kellon, VMD
Empire Saddlery
English Riding Supply
Enrico, Inc
Equerry.com
Equi-Natural Products
Equibrand
Equilite
Equine America
Equine Gold
Equine International, Inc
Equine Rescue Net
Equine Science
Equine Therapy
Equestrian International Products
Equestrian Land Conservation Resource
Equustall Stable Flooring System
EQyss Grooming Products, Inc
Espree Animal Products
E-Z Rider Equine Products
Farnam Companies, Inc
Feedmark
Ferris Fencing
Figuerola Laboratories
Finish Line
Flair
Fortius Natural Nutrition
Foxden Equine Nutrition & Therapy
Foxwise Products
Gardner Fence Systems
G. Passier & Sohn
Geier Glove Co.
Giddyap Girls Biscuit Company
Global Herbs
Glover Equine Products
Grand Meadows
Grand National and World Championship Morgan Horse Show
Groomer's Stone
Hamilton Horse Cookie Company
Hamilton Products
Hawthorne Products Inc
HerbalCom
Hilton Herbs
Horse Breed Associations
Horse Cents Software Company
Horse Fence Direct
HorseHerbs.com
Horses Prefer
Horse Sense Equine Products
Horse Tack Review
Horse Tech, Inc
Horseware Ireland
Hoskins Manufacturing Co.
Hubbard Feeds Inc.
Hug Closures
Humane Mfg.
Humane Society of the United States
International Arabian Horse Association
Ironbuilt Steel Buildings
Jack's Mfg., Inc.
Kentucky Equine Research, Inc
Keratex, The Hoofcare Experts
Keystone Steel & Wire
Kinetic Technologies
King Livestock & Pet Feeds
Lazy Dog Software
Leather Therapy
Lexol Cleaner
Libertyville Saddle Shop
Lucerne Farms
Lucky Braids by Ruthann
Mackinnon, Inc.
Mad Cow Custom Chaps
Manna Pro
March Biological
McCauley Bros., Inc
Miller Harness Company
Miraco Livestock Water System
MoorMan's Equine
Mrs. Pastures Cookies for Horses
MyHorse.com
MySaddle.com
Narrow Gate Tack
National Barrel Horse Association
National Cutting Horse Association
National Horse Show Registry
NaturVet
Nelson Manufacturing
Neogen Corporation
Nickers International, Ltd
Norman Equine Designs, Inc
Peak Performance Nutrients
Perri's Leather and Metal Crafters
Phoenix Sport Horses (John Strassburger)
Pica Publishing
Professional's Choice
ProMat Ltd.
Pro-Tech Livestock Corp.
Purdue University School of Veterinary Medicine
RAMMEquineSolutions
Ration Plus
RB Rubber Products
Rein-Aid Productions
Richdel, Inc.
Ringer Products
Respond Systems Inc.
Rio Vista Products
Ritchie Industries
Royal Riders
Rumber Materials, Inc
Russell Meerdink Co.
Saddle Technology Incorporated
SabreEquine
Safety Products and Equipment
Saratoga Horseworks, Ltd
Schneider's Tack
Schreiner's Herbal Solution
Seaman's Custom Fence
Select the Best
Seminole Feeds
Shapley's
Shoo-fly
Show Business for Dressage Horse Show Management Software
Show Secretary
Skode's Horse Treats
Sleazy Sleepwear for Horses
SmartPak Equine
Smith Worthington Saddlery Co.
Source Biological Fly Control
Southwest Animal Products, LLC
Soy Inc
Spalding Labs
Spring Creek Marketing
SSG Riding Gloves
Star Horse Products
State Line Tack
Sterett Brothers Hay & Feed
Stolen Horse International, Inc
Summit Flexible Products Ltd.
Tack in the Box
Tack Wipes, Inc
TDI Horse Feeds
Tex Tan
The Organized Barn And Trailer
The-Sports-Arena.com
Thornhill
Toklat Originals
Topfit
Triple Crown Nutrition, Inc
Triple J Products
Tuf-Foot
Uckele Health Nutrition
United Vet Equine
USA Equestrian
ValleyVet.com
Vapco
Varnan Waterers
Vets Plus Inc.
Vita-Flex Nutrition
Vita Royal Products, Inc
Watson Gloves
Weaver Leather
Western Saddle Guide
W.F. Young, Inc
Whinny Widgets
Xtreme Design Products