Exercise Demonstration

Click bodypart for exercises that work nearby muscle groups:

To see demonstrations for additional exercises,
check out these websites:

Stretches by Muscle

Be careful not to overstretch, know your limits. Never stretch a cold muscle. These are post workout stretches. Preworkout, you should only do nonstationary stretches (eg. arm circles, bodyweight lunges)

Neck

Neck Retraction
Neck Rotation 
Neck Extensor Stretch

Shoulders

Upright front delt stretch
Lying front delt stretch
Side delt stretch
Rear delt stretch 

Triceps & Biceps

Overhead triceps stretch
Standing biceps stretch

Wrists

Standing wrist flexor stretch

Upper Back

Fixed bar back stretch
Bent over lat stretch (aka extended child) 
Side reach lat stretch
Upper trap stretch
Hugging rhomboids stretch
Doorway subscapularis stretch

Chest

Behind head chest stretch
Doorway chest stretch
Wall shoulder girdle stretch
Doorway modified chest stretch  

Abdominals (stretch with leg workouts as well)

Lying prone ab stretch (aka cobra)
Lying supine ab stretch
Supine Twist (obliques, lower back, glutes)
Seated Spinal twist (obliques, glutes, lower back)
Beginner side angle stretch

Erector Spinae (lower back)

Dog Pose and Cat Pose

Glutes

Lying glute stretch

Hip Flexors 

Kneeling hip flexor stretch
Lunging hip flexor stretch 

Quadriceps

Lying quad stretch or Standing quad stretch

Hamstrings

Lying hamstring stretch 
Seated hamstring stretch 
Standing hamstring stretch

Hip Adductors

Lying groin stretch (aka lying bound angle pose)
Seated groin stretch 
Side lunge stretch 
Lying adductor magnus stretch 

Calves