"Add driver" not on menu I'm trying to add a driver to a shape key but when I right click on the value line, the menu skips "Add Driver" and goes from "Insert Keyframe", "Clear Keyframe", to "Add to Keying Set".  I have Blender 2.74. Thanks.
Thats because you are already controlling the value with keyframes. Drivers and keyframes do not mix.

Select Clear Keyframes from the menu and then add driver.