Discovery Education offers a great collection of free lesson plans about animals, as well as lesson plans on many other science topics.
Teacher Vision features animal lesson plans that include fun, cross-curricular activities for kindergarten through sixth grade. Use these lessons to teach students about mammals, reptiles, amphibians, birds, and invertebrates.
Teaching Pre K-8 Magazine is an award-winning professional development-based magazine for teachers in kindergarten through eighth grade that is now celebrating it's 35th year of publication.
TeAchnology.com offers teachers free access to thousands of teacher resources.