The criss cross stretch is an easy stretch for your back, abs and hips. It feels great. I do this a lot while I am sitting on the ground.
Sit with your legs crossed in front of you. Keeping your torso upright and the top of your head in line with your tailbone take your right hand to your left knee and place your left hand on the ground behind you and slowly twist. Remember that you want to stretch only to where it feels good. Take two deep breaths and switch sides four times. For a more advanced stretch, sit in lotus position (which is legs crossed with ankles on top of your crossed legs).