You can go to amazon and search foam roller, or even google. It's a roller that you use to stretch with and it also helps with core strengthening.
You can lay on it longwise, in other words so that it runs down your back, and then work on try to balance on it, lifting first your arms, then trying to lift your arms off the floor, plus a leg at a time. I guess some people get good enough to balance without their arms or feet touching the floor (but not me, LOL.)
A stretch I love is to place it horizontally on the floor and then lean back onto it and try to let your head touch the floor (arms behind your head as in a sit up position.) You start with the roller a couple inches about your waist, and every set, move the roller up a few inches till you end with it up above your shoulder blades. My spine sounds like popcorn when I do that stretch.
Another thing you can do is lay on your side, place the roller horizontally under your knee, then move your body so that the roller massages the muscles on the outside of the thigh (ouch)...you'd be surprised how many tight spots there are in there.
I googled and found this page showing a guy doing some of the exercises with a foam roller:
http://www.sheboyganfalls.k12.wi.us/staff/...oamrollerex.htm