When I look in the mirror I usually see a pretty big neck, so I figure most guys will get away with no direct neck work if they are shrugging, benching, rowing, etc. with free weights.
One good light rehab style exercise that is good is just take a small plate (10 lbs or 2 X 10 lbs) and wrap in a towel, then lie face down with head off the side of the bed... wrap weight on back of head and gently lift up and down...
Go easy on direct neck work if you don't really need it for sports. Too much compression here can screw up the spine, cause nerve irritation, etc.
Also, avoid car accidents.