Can human hand move at a speed rate like this baseball pitch or is it just the speed of ball? The fastest baseball pitch ever recorded was in 1974 at a speed of $100.9\frac{\mathrm{mile}}{\mathrm{hour}}$ (see correction below).  Does this mean that the pitcher's hand was also traveling at that speed or just the ball?
Is it physically possible to move hand/leg at that speed?
I'm asking this because basically pitcher's hand was moving 17.7 inches per 10 millisecond which is really a super(unbelievable) speed for human.

Update: The figure originally given in this question was dated; a current record of $105.1\frac{\mathrm{mile}}{\mathrm{hour}}~\left(169.14\frac{\mathrm{km}}{\mathrm{hour}}\right)$ was set by Aroldis Chapman in 2010 (source).
 A: I know little about baseball, but if you are willing to extend your question to include God's own sport of cricket, the fastest speed recorded by a bowler was 100.3 mph. This speed was recorded at the moment when the ball leaves the bowlers hand (the ball slows down once it's released) so the bowler's hand was indeed travelling at 100.3 mph.
As Alexander points out, you can attain these high speeds using leverage. A typical fast bowler's arm is around a meter long from the shoulder joint to the cricket ball, and the rules demand the arm be kept straight during bowling. Dividing the speed by the circumference of the circle traced by the arm give the rotation speed as one rotation in 140ms, which isn't superhumanly fast. It's certainly faster than I can manage, but then I'm not paid millions of pounds per year to play cricket!
A: "It's all in the wrist" as they say.. yes, of course the hand connected to the ball was moving at this speed (or higher) at the time of throw. 
This is the same in many other sports like volleyball or tennis. Untrained athletes keep one or more joints stiff during the movement which means they lose the maximum speed and also risk injury due to the added inertia of the arm that has to be accelerated by the shoulder muscles.
A good throw or volleyball spike works by folding the arm into a smaller shape in the beginning of the throw, which reduces the angular inertia allowing the shoulder to accelerate the upper arm. After a while, the upper arm muscles start to accelerate the lower arm + wrist combo, with the wrist a bit twisted, reducing that inertia. And finally the wrist is accelerated by the lower arm muscles. All these accelerations add up to a huge speed at the wrist-end.
Check out the hit at 0:29 in this beautiful slow-motion video
A: Yes, the hand is moving the same speed or faster. And the fastest pitch is not 100.9, I've seen 103 range in person and the record is 105.1. 
