Good thread. Can't believe ATMR is beating me in the Atlami dept. I'll have to follow this more clearly.
I'll start off by covering the Murali. Murali's uniqueness comes from the fact that he can straighten his arm (as much as his congenital defect will allow) and then flex his hand to the degree that his palm would touch his forceps. Freaky!
So what it lets him do is bowl finger spin as well as give extra RPMs and that jerk that gives a ball bounce - all without straightening his elbow.
You can test this very easily. Take a tennis ball, hold in an offie grip and hold it with the ball and your palm facing you. Now flick the ball forward and simultaneously impart finger spin. What you'll notice is that depending on how you flick it or the angle, you'll get very sharp turn and bounce in a direction opposite to the direction you expect. Try the same with a leggie grip and bam you now know how to do the pehla and doosra ala Murali.
Of course this is with you liberally straightening your elbow. Now try doing in a bowling fashion from above your shoulder and you'll find it well nigh impossible to do so without chucking.