US Department of Agriculture
Usda: National Agricultural Statistics Service
A good site for statistical evidence of the importance of domesticated mammals in feeding this country. Click on any of the animal types and you can retrieve how many were slaughtered.
CK-12 Foundation
Ck 12: Life Science: Importance of Mammals
[Free Registration/Login may be required to access all resource tools.] Mammals play many important roles in ecosystems, and they also benefit people. Learn more about the importance of mammals in this learning module produced by CK-12.
Oklahoma State University
Oklahoma State Univ: Breeds of Livestock Other Species
This is a good overview of the use of "other species" that one would not immediately think of as a domesticated mammal. Examples include Buffalo and Llamas.
US Department of Agriculture
U.s. Department of Agriculture: Bats Can Be Farmer Friendly!
Learn about bats and how they are useful to farmers.
Other
Canadian Federation of Humane Societies: Marine Mammals in Captivity
An article expressing concern about the use of marine mammals in the entertainment industry.
Other
International Marine Mammal Project: Dolphin and Whale Project
A site authored by the trainer from the original "Flipper" TV show. This site takes the approach that the exploitative use of marine mammals should be stopped.