There are a number of notification services online that provide the ability to track horses for free and send an e-mail when that horse is entered to run in a race. These services are an invaluable tool for handicappers and owners who want to keep tabs on certain horses.
From Bloodstock Research. Stable Alert is probably the most timely and reliable of the horse watch services. Especially with regard to workout information. There's a free horse watch that lets you track specific horses and a trainer watch which will let you follow specific trainers.
Provided by Equibase & Trackmaster. Virtual Stable will allow you to track horses entered in a specific race. It's quite easy to use and requires that you sign up first. It's free and allows you to keep track of notes for all of your horses. Users have the option of following workouts or results.