Here in the UK the Royal National Institue for the Blind (RNIB) publish some useful stuff on web accessibility (
http://www.rnib.org.uk/digital/)
They have a hints page at http://www.rnib.org.uk/digital/hints.htm and recommend the Web Accessibility Initiative (WAI) which is part of the W3C I believe.
Interestingly, the RNIB quote the UK's Disability Discrimination Act and I think they are looking for a high profile site to tackle with a legal case. It may be that in the near future disability access may be a legal requirement, at least in the UK.
Steve