PAS78 is a new web-accessibility specification from the BSI. Not a standard as yet, but may become so over time. Seems to cost £30 though, even if you download it.

Details here:
http://www.theregister.co.uk/2006/03/10/bsi_disability_guidelines/

Available from:
http://www.bsi-global.com/ICT/PAS78/index.xalter