You can see a foam roller here on the left of this text <---. A foam roller is essentially a dense foam cyclinder that you use as your personal massage therapist. It is used to release the tension/adhesions between your muscles and the facia under your skin that cause you to ache and feel tight. It can also be used to mobilize certain areas of the spine - the thoracic and mid-thoracic, but avoid mobilizing the lumbar spine if you have any low-back issues like I do.
For me, when I get out of bed, I use my foam roller on my quads and hamstrings to release the tension that results of sleeping statically in my oh-so-favorite curled-up fetal position. I also roll my upper back (the thoracic spine) which results in a nice release of the verterbrae and upper back muscles.
When I don't have the opportunity to foam roll in the mornings (which has been the case these past few weeks of my dissertation project - too many really early mornings), I can feel the tension in my body all day long. As soon as I get home though in the evening, I roll for a few mintues and feel much better.
Foam rolling to feel better and attack those tight muscles and static joints doesn't take much time, and it results in so much relaxation. Sometimes you may want to spend a lot longer foam rolling, especially after you've had a hard exercise session and all your muscles need some attention. Like I said, think of your foam roller as your personal masseuse, but it's a lot less expensive.
You can roll your calves and hips after a long run outside, your upper back and pecs after a hard upper body workout and your glutes after a hard hike or leg workout. In the video I found here on youtube, the female trainer does a fairly good job at demonstrating how to benefit from a foam roller. Here is the link for a visual:
Then, to learn more about the foam roller, read this article by my good friends Eric Cressey and Mike Roberts, published on t-nation.com, "Feel Better for 10 Bucks"
Mike Boyle also has an excellent DVD available at Perform Better.
Finally, to get your own foam roller, check out here. I've got the new PB Elite Molded Foam Roller, and it's much better than the traditional Bio-Foam Rollers that tend to compress over time.
Now, after writing about this, I'm going to go roll my glutes... I've been sitting on them too long today. :)