Jonathan Lampel hosts a look at using multiple particle systems in Blender on blender Diplom, to create realistic animal fur, walking though how to create fur materials for rendering with cycles.
Learn how to add great looking particle fur for any animal
This two-part tutorial provides a little overview and shows how to create fur for the body of an animal, and how that differs from creating facial fur, whiskers and ear hair. Jonathan shows how to create a shader for cycles that will give realistic results, using the hair particle system that was added to Blender 2.69.
Check out the Blender tutorial for Creating Fur and Particle Hair with Cycles here.