Here's one that will gives you a good release in your lower back, shoulders and neck by gently twisting. It can be instant relief for back and shoulder strain. I use it a lot as an office break.
Don't do this is you're pregnant or have issues with the bones in your spine, (like arthritic spine, osteoporosis or a fused spine).
Start
Sitting in your chair
You can sit facing forward, with your back into the back of your chair
Or you can sit sideways in your chair, with the back of the chair along your arm & side.
Make sure you are settle squarely into your chair, legs, hips, back and neck lined up with each other.
Now turn your body toward the back of your chair.
Hold on to the back of your chair with both hands, (hands at the same side of your body. See picture.)

As you breathe out, start twisting.
To encourage the twist, use your hands to push against the back of your chair.
Start the twist by turning at your waste.
Then keep going by turning your body.
Then keep going by turning your shoulders.
The turn your head as far as you can - without pain!
Stop before anything hurts!
Tip: If your neck is sensitive, then don't turn it too much, or don't turn it at all.
Hold it for a breath or two.
Then slowly undo the twist by reversing your movements.
Take the time to wait for the stretch to release completely before doing it again. (Wait until all your muscles let go of the stretch before repeating it.)
Do three times. Then switch sides.
Breathing
To get the most out of this exercise, twist while you're breathing out, then pause as you breathe in, then continue the twist as you breathe out. (Going along with the
Relaxation Effect.
Don't force your breathing. Just long, slow, lingering breaths out. Breathing about 2/3 full and about 2/3 empty.