Hidradenitis Suppurativa Foundation: 
http://www.hs-foundation.org/

Canadian Hidradenitis Suppurativa Foundation (CHSF): 
http://hs-foundationcanada.org/en/home/

American Academy of Dermatology - Hidradenitis Suppurativa:
https://www.aad.org/public/diseases/painful-skin-joints/hidradenitis-suppurativa

The Hidradenitis Suppurativa Trust
http://www.hstrust.org/

HS Online (Canada):
http://www.hsonline.ca/

HS Online (United Kingdom):
http://www.hidradenitissuppurativa.co.uk/