How to animate a tail
-Place a null at each joint in the tail.
-Create a position constraint for each null - the joint being the constrained object and the null the source.
-Now use your nulls in a "waggy tail" relations setup (as described in the buzz vtms on constraints)
-Be sure to parent your first null to the hips.
-Now in order to manipulate your tail directly with the nulls, Select your character in the character controls, click on show and uncheck "Skeleton Lock Trs"
-The stiffness of the tail is controlled by the value you set in the damping factor of the waggy tail relation(lower = stiffer)
Problems with this method - mainly that the tail stretches with high damping values. I'm sure this can be corrected with additional constraints or translation limits.
Remember that the quality of your tail deformation will depend on how many joints are in your tail and how carefully you've skinned it.