The plank is a great exercise for isolating your abdominals. It might not have the flare and burn rate of some other often performed stomach exercises but it is just as effective. There are also variations that isolate the obliques (a.k.a., love handles).

Benefits:
This exercise contributes to a strong core area (abdominal's, chest and back muscles). It forces you to support your own bodyweight at four points - your two feet and your forearms. Be sure not to drop your hips when performing this exercise because that could put a strain on your lower back.

Equipment Needed:
Planks can be performed without any equipment, but a padded exercise mat may feel better on your elbows.

How to Perform the Plank:
Lay with your two feet close together and place your elbows on the ground or mat (or exercise ball for advanced exercisers) about shoulder width apart. Lift your body off the ground with your abdominal muscles. Hold this position.

Picture courtesy of hitechtrainer.com. Software provider for Tetro Performance online services.

Other Notes:
Try holding this position for at least 30 seconds. Keep your back straight and hips up. Add time as you progress.