Shape Keys plus Armature I have already rigged a character in blender. 

I am trying to create viseme's using Shape Keys. The shape of the mouth is dependent on the jaw position. Most of the viseme's happen with my characters jaw is open.

So I rotate the jaw, select the mesh again, and add a new shape key. When I do the jaw will snap back to its closed position. I can't do the shape key while its mouth is closed.

I tried this several ways, the other way is you create a shape key, go into edit mode and then try to shift the jaw, which just closes the shape key.

Is there a way to combine the shape keys (mouth shape) and armature (jaw)?
To view the deformation by an armature in edit mode you have to check the two options of the armature modifier (1) Display modifier in Edit mode (2) Adjust edit cage to modifier result. They're located next to the visibility icon. This allows you to edit the mesh in its deformed state. – Leander Sep 18 at 10:14