I am doing GB program: Foundation 1, Handstand 1, with the Front Splits, Straddle Splits & Thoracic Stretch Series.
I mainly started so that I could get better at walking on my hands for the 10th Planet Warm-ups, but in the process discovered a lot weaknesses and mobility issues I had developed elsewhere. I highly recommend the program it is very challenging. No more Shoulder, Neck and Back issues for me after doing this for about 9 months now.
If you are on a budget I have also found that Ido Portal stuff to be very similar, just a little less structured than the GB program.