The AllBreedPedigree.com website has extensive standardbred bloodline info and you can input new harness horses to help keep it up to date.
All Breed Pedigree Database containing more than 1 million horses from all breeds. Get pedigrees reports and a free five generation pedigree chart.
If you have a slow Internet connection this next link may be ideal, as it allows you to immediately download the full ClassicFamilies.net database for a 10-day, no obligation free trial. Extremely useful for standardbred maternal family research and harness horse sireline cross research. If you decide to upgrade, you'll get an even newer database, but for most people the free one will be very helpful.
The Classic Families of the Standardbred horse racing breed. Download a FULL copy of Classic Families and use it for 10 days free.
The StallionDatabase.com is an excellent guide to pacing and trotting stallions in North America, check it out:
Harness bloodline. the FREE online stallion database ... Click on a horse name from anywhere on the site to access respective stallion profile. ...