It's a really bad thing to have a busy day ahead and wake up with cricks or cramps in your neck. It can ruin the morning before you even get started. Many times you will wake up with a sore neck simply because you are sleeping on the wrong kind of pillow. If you have had a neck injury that causes you pain, your pillow is even more important.
Many have found that sleeping on a solid memory foam pillow can be very beneficial. A solid foam pillow will hold a consistent shape throughout the night and provide your neck with the constant support it needs. Cariloha makes an excellent bamboo gel memory foam pillow. Ergonomic has a cervical pillow for neck pain that also works works well. They shapes are similar.
However, these pillows might be a little too firm for some people. If you like a softer pillow, you might try one made from shredded memory foam instead. It's easy to compare many memory foam pillow types when you visit a site like Luxury of the Pharaohs. It is where I found my perfect pillow and I no longer wake up with that horrible neck pain anymore. I go to sleep and stay asleep for hours. I have not rested as well in years!