In what would be a great step for fans, Robin over at Thorobase seems to be working on a video catalogue of great horses and great races. It looks to be searchable as well. I like a lot of you, have searched for horse racing video many times on the web, and it seems to be more mixed up than a drunk baker. In addition, not long ago (if we can believe it), horse racing videos were taken off the web because of some sort of arcane 1847 rule on copyrighting or something. I remember going one day to watch the Florida Derby on youtube and the next day it was gone, never to reappear.
If you'd like to be kept updated on the project you can via an email box on the site. As fans we can get lost for hours on old video, if it is categorized and labeled properly. Let's hope this helps!