National Center for Accessible Media
http://www.wgbh.org/wgbh/pages/ncamGuidelines for accessible media, audio description and web development.
USABLENET
http://www.usablenet.com(415)336-9437 (Customer Service)
508 Accessibility Suite for Dreamweaver and ultraDev
Dreamweaver and UltraDev evaluation tool allows web site to be accessibility checked much in the same way as you spell check in a word document. The extension covers Section 508 and level I W3C/WAI guidelines.
W3C Recommendation for Web Content Accessibility Guidelines 1.0
http://www.w3.orgIndustry leaders and disability organizations come together to endorse a common solution for web access.
Web Accessibility Initiative (WAI)
http://www.w3.org/WAI/Strategies, guidelines, resources to make the Web accessible to people with disabilities.
WebAIM
http://www.webaim.orgProvides up-to-date information for those interested in providing accessible web pages and web content.