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