I've always worked my forearms hard. Out of vanity, and the fact that in most instances people could not see your biceps, but often could see your forearms I've always trained them hard.
My favorite exercise is the reverse curl. But do it with an EZ Curl bar or your wrist might start hurting. This not only works the forearm, but also a small knot of the biceps where it attaches to the forearm muscle.
Hammer curls. Also very good. And I always do both. There is a large overlap on the reverse curl and hammer curl as to effect. If you have access to an incline board try hanging your arms plumb (straight down) and doing the hammers. This will lengthen the biceps as well.
Grip exercisers. I have one from Iron Mind. They are the only ones really worth getting. But don't be overly ambitious. Their weakest one is way tougher to use than the heaviest ones you find in the sporting goods stores: http://www.ironmind.com/ironmind/opencm ... crush.html
Grip the gripper with the coil at your thumb end of the hand and then reverse it so that the coil is at the pinky end of the hand. This will assure that you involve all the fingers in the exercise.
I used to do upright rows with two 45 pound Olympic weights. Old style Olympic weights had a lip on one side and a smooth surface on the other. I would place both lips together so only the smooth surfaces were available to grip. Using friction only I would do the upright rows. I'm not certain how effective this is as a training method as it is essentially an isometric exercise. But is is very tough to do and I liked showing off.
Finger tip push ups. I used to do 20 or so on all ten finger tips. I could do 2 or 3 using only my thumb and pointer fingers of both hands.
Finger tip pull ups. This was useful for my (at the time) rock climbing. Find a commercial door with a steel buck (steel frame around the door). The buck usually extends about 1/2" from the wall. Curl your four fingers (no thumb) on both hands to grip the top of the steel buck (leave the door open so you can hang). Then do your pull ups. But don't do this on your home door as the wooden molding will peel off the wall.
Avoid using lifting straps for your lifts as it will leave your forearm undeveloped.