There are about 50 muscles in our head & neck alone!
After years of massage and my own experience of stress in my body, two important muscles to massage in the neck are the SCM (which is the sternocleidomastoid) and the scalenes.
First, the SCM (sternocleidomastoid) gets its name from: sterno which refers to sternum, or breastbone, cleido refers to clavicle, or collarbone, and mastoid comes from attaching to the mastoid process which is the bony knob behind the ear. This muscle gets used when leaning one’s neck forward looking at the computer or with any activity where one leans the head forward, i.e. looking at your blackberry. Also, anyone who slouches are habitually leans forward will experience pain here. These are the muscles that can pull so tight they can cause a hump behind the neck (when they are not released). (This happens over an extended amount of time.) The stress put on this muscle can cause trigger points which can cause various problems ranging from sinus tension, sinus congestion, headaches, ear aches or flutter in the ear, jaw tension (which is sometimes misdiagnosed as TMJ) and even dizziness. They can refer pain to the back of the neck and top of the shoulders, too. The list goes on, yet you get the idea of how powerful of an effect this muscle can have when it is taxed.