Web Content Accessibility Guidelines 2.0
- A W3C working draft for an updated version of their accessibility guidelines.
- http://www.w3.org/TR/WCAG20/

WCAG Samurai
- A group of developers, led by Joe Clark, that worked on corrections for, and extensions to, the Web Content Accessibility Guidelines 1.0. Includes published errata, and links to independent reviews of their work.
- http://wcagsamurai.org/

Web Content Accessibility Guidelines 1.0
- Recommendation from the W3C, which explains to developers and authors how to make Web content accessible to people with disabilities.
- http://www.w3.org/TR/WAI-WEBCONTENT/

Section508.gov
- Official website for Section 508 of the US Rehabilitation Act.
- http://www.section508.gov

PAS 78: A Guide to Good Practice in Commissioning Accessible Websites
- A Publicly Available Specification from the British Standards Institution, in association with the Disability Rights Commission. [free download subject to some license conditions]
- http://www.bsi-global.com/en/Standards-and-Publications/Industry-Sectors/ICT/PAS-78/

Illinois Web Accessibility Standards
- Official state guidelines. Readable format with an explanation and implementation tips for each item.
- http://www.illinois.gov/iwas/standards/iwasStandards.cfm

Government of Canada: Accessibility
- Official standards and guidelines for Government of Canada Web sites, as part of the Treasury Board's "Common Look and Feel" initiative.
- http://www.tbs-sct.gc.ca/clf-nsi/inter/inter-01-tb_e.asp