I have Pocket Yoga for my iPod.
It has pose descriptions, 3 classes, each with 3 levels (beginner, intermediate, and advanced, that you can do for 30, 45, or 60 minutes each). Plus, they recently added "Sun Salutation" sequences - quick stretching workouts you can select by number of repetitions (2-30). Those will give you a quick 15 minute wake-up session....