Hi,
As I was working on some code for real time character animations I wrote some documentation to help me understand it better (a little trick that never fails me).
Anyhow the result is a 4 page pdf tutorial on how to rotate the different bones of a skeleton efficiently. Use it any way you want, remarks are always welcome (English is not my native language so go easy on me).
Erratum 1: made a mistake on page 4, third translation should be : Translation : T3 = (W-E)q2q1 + T2
Erratum 2 : changed total rotation to global rotation
Koen