RNIB - Royal National Institute for the Blind
British Dyslexia Association - Good information about how people with dyslexia process information and use the internet.
RNID - Royal National Institute for the Deaf
GAWDS - Guild of Accessible Web Designers
Ability Net - A leading authority on accessibility. Provides training and equipment to people with disabilities and consultancy services to businesses.
UAWG - The Usability and Accessibility Working Group has been established to create an accreditation scheme to identify qualified designers. The site also has information on accessibility and usability.
Web Standards Project - Trying to develop standards for web design, browsers, plug-ins and extensions to make surfing the internet easier for everyone.