I've been involved in BDSM and ponyplay for over 10 years, and during that time I have owned and tried a fair amount of equipment. I offer my opinions here about some of the equipment I've bought and used over the years. Ponyplay equipment is usually expensive, unfortunately it is not always well made, so I hope my thoughts can help you when choosing items for your tack box.
Current Products
The Pegasus 2 Equine Sheath - The second generation Pegasus equine sheath is a horse cock shaped silicone toy that is designed to be worn over male pony's own penis or a strap on. Additionally it can be used as a dildo or a masturbation sleeve. The changes over the original Pegasus include a redesigned ball strap, which holds the Pegasus more firmly against the body (so well in fact that it feels like the Pegasus 2 is a part of your body), a thinner shaft wall (to better communicate stimulation), and a lengthened interior. Also new is the availability of more color options, incuding a natural coloration.
The Derby - This is a knee high pony boot made by Punitive Shoes and marketed for ponyplay. It comes complete with an aluminum horseshoe and is available in black, red, or white leather with either patent or matte finish. I would classify this as a bondage hoof boot since it is very restrictive and could almost be classified as a ballet boot.
ErosTek ET232 Power Unit - The portable power box, the ET232 by ErosTek, is a full featured e-stim unit that can be easily attached to pony't harness. While it is not remote controlled, the unit is great for treadmill and cart training (or anywhere you are not too far away from your pony), and it can be used for reward or punishment. The subjective feeling of the 11 preset stimulation modes can be adjusted by the "MA" knob (as well as the intensity knob) and can provide sensations anywhere from the painful stinging of a shock collar to a gentle stroking.
Bob Basset Horse Mask with Long Mane and Application - A leather full head coverage pony mask with a long mane and decorative leather applications. This is a beautifully crafted horse mask that is fun and comfortable to wear for long periods of time. Although expensive in absolute terms, it is fairly priced in comparison to smimlar products. The main drawback is how quickly the inside of the eyes fog up from the moisture of exhaled air.
The Human Pony (book by Rebecca Wilcox) - Currently, Rebecca Wilcox's book "The Human Pony" is the only reference book available on pony play. The book is a well-illustrated introduction to the world of human ponyplay. While the book will be of particular interest to those lacking bio-horse experience, I think it does offer useful information for anyone interested in ponyplay.
Rubber Hoof Gloves - The Fetisso brand hoof mitts are sold by quite a few retailers of bondage equipment. These are simply molded rubber hoof shaped gloves. While almost like a fist mitt the elasticity of the rubber does not completely prevent the wearer from opening her hand while wearing it. However, on the flip side, the elasticity of the rubber does make them fit quite snugly around the forearms making them somewhat difficult to remove if the wearer has one on each hand.
Rosebuds Horse Hair Plug Tail - The solid steel plug portion is designed by Julian Snelling and is very well made and has a rather tasteful look with the bronze petal base. The tail is real horse hair and is very well attached to the plug. As someone not generally into butt play, I was surprised to find myself buying the version with the larger plug portion. However, I don't regret my purchase, and while it a little on the expensive side, I could actually find no real issues with the Rosebuds tail.
Sinvention Pony Point Trainers - My first ever order from Sinvention, The pony point trainers by Sinvention are a great way to teach your ponyboy to stay on his toes when you don't want to whip out the hoof boots. If he fights them and tries to lower his heels, the pony point trainers are incredibly painful, but if he doesn't fight them, they are wonderfully comfortable and more than a little arousing to wear.
Sinvention DeLuxe Leather Lined Pony Breeding Hobbles - After admiring the Sinvention pony play hobbles for quite awhile (for quite a few years actually), I finally found the opporunity and the motivation (in the form a sale) to buy a pair. There's lots to love about these hobbles, but my favorite is the combination of the elegant, locking leather cuffs contrasted with the utilitarian, genuine livestock grade chain that joins them together.
Leather Hoof Mitts - This is really a review of leather puppy fist mitts which I converted into a pair of hoof mitts complete with a horseshoe.
Pet and Ponygirls - Not an equipment review, but petandponygirls.com is a site to which I have subscribed in the past. I enjoy their content and thought I would write a quick review. They are a subscription site that offers still and video content of females as pet and ponygirls (hence the name). With a plethora of free content available, pay sites have to go above and beyond in quality to justify the price. In my opinion, petandponygirls is one of the few sites that does it right.
The Riding School (Book 1) - A work of erotic fiction for the BDSM pony player, this first installment of a series was quite well written and had me aroused for most of the 5 chapters. The author clearly spent some time researching items of tack for bio-horses and human ponies. It made for a good read, but it is part of an installment series, so it ends a little abruptly (which is not unexpected from the book's description).
Pony Training: 5 Case Studies - While it would seem that this book offers some insight and discussion on the mindset of pony players through a series of interviews, the book is nothing more than 5 ponyplay stories taken from SirJeffs and/or other free story websites. It is certainly not worth spending your money on, and the original authors of the stories are not even credited.
Discontinued Products
The Pegasus Equine Sheath - The Pegasus equine sheath by Fetishzone, is a wearable horse cock for male ponies: it is a scaled down (but still far from small) horse cock shaped sleeve that fits over the wearer's own cock. It gives the visual appearance of the wearer having his own horse cock, while still communicating physical stimulation through the sleeve to the wearer. This version of the Pegasus has been discontinued and replaced by the Pegasus V2 equine sheath.
Reactor Rubber (Kaysers) ponyboot - Reactor Rubber (formerly Kaysers) have had on and off production of ponyboots with a slightly more realistic "hoof" than some of the others out there. Unfortunately, it seems that they have permanently discontinued their ponyboots. In fact, it seems Reactor Rubber (formerly Kaysers) is no longer in business, and the Strangeglove Clothing Company (founded by the former owner of Reactor) may also be closing their doors soon. This is quite unfortunate since they, along with Reactor, have produced some great products over the years.