If you are involved with an NGO for the disabled, read Chapter 2 of folder How to Build a Good Small NGO . It discusses the importance of involving and respecting beneficiaries.
folder Interviewing & Counselling at the Grass Roots includes a section on recognizing and helping people with disabilities.
A practical manual:
folder Simple Devices to Assist the Physically Disabled has dozens of self-explanatory drawings for making devices from scrap materials