While I do not specifically work out my forearms on a regular basis, I find that much of my workout routine hits the forearms anyways. Reviewing my article How to Get Big Arms: Muscle-Building Exercise Routine for the Biceps, the three supersets on my Biceps Power Day really hit the forearms. Doing Bicep Curls for 15 reps makes the forearms burn. Hammer Curls are another great way to work out the forearms. They are Dumbbell Curls in which the palms face inward the entire time and you do not twist your wrists. The dumbbells will be vertical as opposed to horizontal at the top of the movement. Anything that involves you gripping or moving heavy weights will work out the forearms like Deadlifts, Lat Pulldowns, heavy Upright Rows or Calf Raises on a calf press machine.
Your bicep workout can be altered to include more forearm development. For instance, Reverse Curls are performed just like Bicep Curls except the palms face in the opposite direction. The disadvantage to this exercise is you will not be able to do nearly as much weight as with regular Bicep Curls.
The bread and butter to any forearm strength training are Wrist Curls. I occasionally add three sets each of Dumbbell Wrist Curls and Reverse Dumbbell Wrist Curls after my biceps and triceps routines. I much prefer using dumbbells over a barbell because dumbbells allow me to concentrate on one forearm at a time. They allow for a fuller range of motion as your wrists naturally twist slightly higher on one side over the other. The restrictive nature of the bar will limit this range of motion. Finally, your stronger arm will not be carrying your weaker arm when you do each arm individually.
I find my Bowflex SelectTech 552 Dumbbell set to be very useful for both Wrist and Reverse Wrist Curls because I can adjust the weight so that one side of the dumbbell is heaver than the other. For a full review on adjustable dumbbells you can read my article The Advantages and Disadvantages of Bowflex SelectTech Dumbbells.
If you want to use a barbell for adding power exercises for your forearms, I recommend Behind-the-Back Wrist Curls. Hold the bar with your arms rested behind the back and curl the weight upwards as far as you can with your wrists while keeping your elbows steady. A similar type of movement can be done to work out the forearms on the backhand side by holding the bar in front of you and curling them upwards. While I find both of these exercises useful, as mentioned before they don't allow as great of a range of motion as Dumbbell Wrist Curls.
Refer to my other workout articles if you are interested in:
More of my workout advice:
Are Bowflex SelectTech Adjustable Dumbbells suitable for you?
Should you buy Bowflex SelectTech Dumbbells in a store or online?
Why you would want to use barbells for your workouts
Why you would want to use dumbbells for your workouts
How I lost over 40 pounds in 6 months with some simple diet changes
Upper body exercises with no equipment needed
Lower body exercises with no equipment needed
Cardio exercises with no equipment needed
The Different Ways of Doing Dumbbell Bicep Curls
Inflatable Exercise Ball Exercises for Men