Oklahoma State University
Oklahoma State University: Breeds of Livestock: Descriptions and Pictures
An impressive database of breeds, with descriptions, photographs, history, and references. If you want to market livestock, this will be invaluable information.
Careers New Zealand
Kiwi Careers: Livestock Agent
This site provides good beginning information about the job, but with the understanding that the specific information such as salary, etc., is from New Zealand. Use the navigation bar on the left to see more information.
Other
National Association of Animal Breeders Resources
While the page says that it is for the serious breeder, there is also information suitable to someone curious about livestock careers, especially breeding.