Workout: 

Slide two lacrosse balls into a long sock.
Tie a knot to hold the balls in place at the bottom of the sock, making sure there is not any loose fabric around the lacrosse balls.
Lie on your back with your knees bent and feet flat on the floor
Slide the lacrosse ball under your low back so that each ball is one either side of your spine
Make sure that neither ball is pressing directly on the vertebrae of your spine
Your spine should sit comfortably between the two balls
Find a point of tension and hold that position for 1-2 minutes, or until you feel the pain release
Then move the balls up your spine a few inches repeat
Repeat this going all the way up your spine. 
When you have finished your entire spine, you can return to any specific points you remember being especially tight. Hold the lacrosse balls on that point of tension until it releases, then repeat going two inches above and two inches below that point of tension. 

This tool is compact and small enough to bring with you anywhere! I love bringing it with me when I travel because I get so tight after plane rides.