I am sure that you have seen those expensive back massagers. Well why not make your own. Simply put several tennis balls into a long sock, tie the end up and you have a great back massager. Another one you can try is simply rolling up a towel into a sausage and tying it with string.
To use either of these massagers you just place them on the floor and slowly move your back along over the massager. This is great for improving suppleness and circulation