for one, thick traps can give the illusion of a big neck..that being said, do barbell shrugs (hands side by side or shoulder width) and/or dumbbell shrugs...as for direct neck related exercises, some gyms have the machine where you just apply resistance to the pad...personally I will take a towel, fold it into a little pad and put it on my forehead (or sides, depending on what I'm working) and then place like a 25 pd. dumbbell and do raises...look like a douche bag but gets it done...
hope that helps
peace,
CN