Animal Photos is a great source of Creative Commons licensed photos of animals. All of the photos are categorized by animal. Each image indicates the type of Creative Commons license associated with the picture. Animal Photos also offers advice on giving attribution for each photo.
Picture Source: doviende
and Animal Photos!

Applications for Education
Animal Photos could be useful for students creating digital presentations for science classes or for any situation requiring an image of an animal.

Here are some related resources that may be of interest to you:
William Vann’s EduPic Graphical Resource
Compfight – Creative Commons Image Search