The W3C Web Content Accessibility Guidelines Working Group has updated three working drafts covering various topics:
"Web Content Accessibility Guidelines 2.0 (WCAG 2.0) covers a wide range of issues and recommendations for making Web content more accessible. This document contains principles, guidelines, and success criteria that define and explain the requirements for making Web-based information and applications accessible. 'Accessible' means usable to a wide range of people with disabilities, including blindness and low vision, deafness and hearing loss, learning difficulties, cognitive limitations, limited movement, speech difficulties, photosensitivity and combinations of these. Following these guidelines will also make your Web content more accessible to the vast majority of users, including older users. It will also enable people to access Web content using many different devices - including a wide variety of assistive technologies."
This draft is in last call. Comments are due by May 31.
This draft "provides detailed information about each success criterion, including its intent; the key terms that are used in the success criterion; examples of Web content that meet the success criterion using various Web technologies (for instance, HTML, CSS, XML) and common examples of Web content that does not meet the success criterion. Finally, this document also explains how the success criteria in WCAG 2.0 help people with different types of disabilities."
"This is a First Public Working Draft of Techniques for WCAG 2.0. It is the first publication as a combined document; previously, techniques were published as separate documents - one for each technology. This document is being published as WCAG 2.0 goes to Last Call. It provides explanation of the techniques documented by the Web Content Accessibility Guidelines Working Group. Some are sufficient to meet a particular success criterion (either by themselves or in combination with other techniques) while other techniques are advisory and optional. None of the techniques are required to meet WCAG 2.0 although some may be the only known method if a particular technology is used."
There's a lot of good information here. These should really be required reading for all HTML authors and web designers. The Techniques spec is probably the most practical, and where most readers shoudl start.