These things are amazing. If you're a runner or serious fitness fiend, you already know about them, but even if you're not, they offer tons of benefits.
I started using them when I developed hamstring tendonitis after Little A was born. But now that I religiously do Essentrics after my workouts, I am pain-free. Nevertheless, I still get tight hips and nothing is better for that then a foam roller.
I recently introduced the roller to some personal training clients of mine who are pretty sedentary and both have quite a few injuries and limitations, which has resulted in a lack of mobility and a lot of tightness and stiffness. They couldn't believe the relief these rollers offer!
So whether your discomfort is due to strenuous activity, or lack there of, I highly recommend you try one. The basic stretching techniques are shown above.
They cost about $40 depending on size and foam density, but are totally worth it (despite the fact it probably costs $0.25 to make them!).