What are those numbers on my OTTB's pedigree? Not the obvious number of races run and money earned (if s/he was lucky enough to be "in the money"), but things like "Dosage Index" "Center of Distribution" etc. In a nutshell, it's basically a mathematical formula that predicts how well-suited a particular horse is to short vs. long distance races (i.e., a sprinter vs a longer distance horse) Here are some links to very good tutorials on those subjects: Clicking on a link will open a new window.
Explanation of Dosage, Brisnet.com (Bloodstock Research Information Services, Inc.) - includes a list of sires that are considered "Chefs de Race" which will add points to a horse's score.
Dosage in a Nutshell, Teamvalor.com
Beyer Numbers, Daily Racing Form - these would be listed next to a horse's name in the racing form and are meant to be a tool for bettors to determine a horse's potential in a given race. The higher the number the better the horse in terms of race class and earnings potential at a given distance and track.
What is an "Allowance" race vs. a Claiming or stakes? What does it mean to be a "Graded Stakes" horse?
Understanding the Types and Classes of Horse Races, About.com Horse Racing
An Explanation of the Graded Stakes Process, Thoroughbred Owners and Breeders Association
Graded Stakes Races (US), Thoroughbred Owners and Breeders Association
You know you have a Thoroughbred that raced, but you have no idea who s/he might be? There is help available! And, even better - that help is FREE. The Jockey Club Information Services offers a tool that can help you to identify your horse based on his or her tattoo. You do need some basic information such as color, sex, markings and some of the letters to use the online tool. If the tattoo is completely illegible, you can take photos of your horse, including photos of the tattoo and good clear photos of distinguishing markings/whorls and send it to the Jockey Club for help. You can watch a video and find out more about the fine art of reading tattoos on the link below:
Tattoo Lookup and Research, The Jockey Club Registry
If you do know your horse's registered Jockey Club name, you can look up your horse's official race record (including charts and videos if the racing was recent, though you do have to pay for the videos) at Equibase.com - this is a free service and it is accurate. You can also look up a full official pedigree at equineline.com for free. Equineline is part of the Jockey Club Information System, so you can be certain it is accurate. There are other pedigree sites out there, but they can be edited by anyone and are sometimes incorrect.
A good article, written by Heather Benson, about ways to look up racing history of your horse - lots of good links and advice in this article: Who Was Your OTTB in a Past Life, HorseNation.com