I can't remember having a neck so stiff that its ability to turn was compromised; however, because I ride a desk 40 hours a week and do a fair amount of computer work my neck and upper trapezius muscles are always in need of stretching. So it's neck stretches, trap and upper back stretches I rely on most, in stiffness and post workout cooldown.
My favorite neck stretch is:
Stand upright, with a good strong torso; bring your right hand back behind you, and grab the right hand with the left. Use the left hand to draw the right hand across the left buttock, while at the same time inclining your LEFT ear down so that it is "listening" to the LEFT shoulder. Hold that position for 10 - 20 seconds, then gently release.
Then repeat on the other side: bring your left hand back behind you, and grab the left hand with the right hand. Use the right hand to draw the left hand across the right buttock, while at the same time inclining your RIGHT ear down so that it is "listening" to the RIGHT shoulder. Hold that position for 10 - 20 seconds, then gently release.
Then, standing back in vertical neutral, let your arms hang down so that the palms are lying on the outer thighs. Gently hang the head forward until you feel a nice pull down the spine, while at the same time "walking" your fingertips down the sides of your thighs to increase the pull. Hold at the deepest stretch position you can comfortably for 10-20 seconds.
I wouldn't be surprised if Cathe herself employs similar stretches in some of her cooldowns; I always "do my own thing" for post-workout stretches so apologies if this is repetitive.
A-Jock