One of the first and still the best for generating 4 generation pedigrees, dosage info, female family reports, and more is the Pedigree Online Thoroughbred Pedigree Database. This database has been around for many years now and while it doesn't include every thoroughbred ever to race, it does have most of them listed now. Originated by Albin Warth over 10 years ago, it was taken over by new owners a few years ago and still offers most info for free with full access available by subscription. It does allow users to add or update info and photos, and it quite complete now.
If you need more info about a horse, you will need to go to a pay service. The reports run from $5 to $10 each depending on what info you want but if you are seriously horse shopping, this information can be invaluable. There are two services which will gladly sell you this info and both are equally good. Bloodstock Research Information Services and EquineLine.com both require that you sign up and give credit card info to get a userid and password to access their service, but if you really need official info or detailed stats this is the only way to get it.
Another great resource I recently had the pleasure of trying out isn't really online although you can read about it and order it online. It is the Thoroughbred Pedigree Reference Sourcebook from Greathouse Publications which traces the sire lines of over 39,000 horses back to the foundation sires. Great for checking out those pesky Phalaris and Non-Phalaris lines for handicapping the Kentucky Derby or seeing just who a particular sire traces back through on the tail male side. All the sires listed are indexed so they are easy to find and the lines are presented in the traditional tree manner. This book should be on every pedigree buff's reference shelf and is well worth the $49.95 price tag.
In addition to these, there are many other very useful pedigree sites and products out there which I have categorized below. Most are for the Thoroughbreds but there are a couple of sites for the Standardbreds and Quarter Horses.
Reference Material
Greathouse PublicationsOffers a great book called Thoroughbred Pedigree Reference Sourcebook which traces the sire lines of over 39,000 horses back to the foundation sires. Very useful book!
Pedigree and Performance in Thoroughbred Racing
From Steve Roman the creator of the dosage index. Lots of good info about dosage, pedigrees, lots of statistics, and more. Nice page.
Ulbrich's Peerage of Racehorses
Excellent books and software on pedigrees.
Werk Thoroughbred Consultants
Pedigree research, analysis, and nick ratings
Online Databases
Pedigree Online Thoroughbred Pedigree DatabaseGet pedigree, dosage info, and stallion progeny for free, other info by subscription.
Action Racing Online Database
South African pedigree database that is very impressive, but is now a subscription service. Slanted to the SAF breds but also have international horses that appear in pedigrees there too. Includes nice detailed profiles of lots of horses with race record, progeny, etc.
Australian Stud Book
Complete access to Australian breeding records, including all named horses, horses sent overseas, imported broodmares, dual hemisphere stallions, and breeding stats. Very informative site.
Bloodstock Research Information Services
Pay service with pedigrees, past performances, and a ton of reports for stallion progeny, broodmare produce, etc.
EquineLine.com
This service from the Jockey Club will give you all kinds of pedigree information for all registered Thoroughbreds for a fee.
Japan Bloodstock
Impressive database of pedigree info and more for horses world wide.
Tesio Power
Computerised database of over 200,000 horses, designed to help upgrade thoroughbred families using Federico Tesio's proven line-breeding guidelines. Downloadable demo available.
Weatherbys Bloodstock Services
This is the online pedigree and racing information service from Weatherby's in England. This service is the equivalent of the Jockey Club in the USA and should have better information on English and European horses.
Stallion Registers
The Blood Horse Stallion Register OnlineLists all active North American sires and their location along with detailed stallion pages for many of them.
Thoroughbred Times Stallion Directory
Includes thousands of stallions in North America and Europe.
New Zealand Thoroughbred Breeder' Association Stallion Register
Really nice with a ton of stats.
Articles
Andrea's ThoropageHorse racing info with and emphasis on pedigree
Astrid Southey Pedigrees
Breeding News and Pedigree information from Australia.
Dosage in a Nutshell
Explanation of the basic concepts of dosage theory and analysis. Find out what all those numbers really mean.
Software
CompuSirePedigree analysis software
M375 Thoroughbreds Inc.
Computerized pedigree research
Tesio Power
Computerised database of over 200,000 horses, designed to help upgrade thoroughbred families using Federico Tesio's proven line-breeding guidelines. Downloadable demo available.
Ulbrich's Peerage of Racehorses
Excellent books and software on pedigrees.
