Without an image to accompany it, I don't really know how to perform this psoas stretch
Stand up straight, and move one foot about 10 inches behind the other. Bend both your front and back knees, evenly distributing your weight between your two feet. Make sure your knees do not extend past your feet, and keep your hips reaching forward. Hold for 20 seconds, and switch feet
From:
How to Stretch the Psoas Muscle | eHow.com http://www.ehow.com/how_2067121_stretch-psoas-muscle.html#ixzz1rbnJfSA8