These are some of our favorite resources.
References / Articles / Blogs
WebAIM - Web Accessibility In Mind
WebAIM offers a wide array of web accessibility services as well as information and resources to help you develop and/or retrofit your site for accessibility. They also developed the WAVE tool for in-browser analysis of your site.
The Accessibility Project
A community-driven effort to make web accessibility easier.
Accessibility Drupal Group
The official Drupal group for discussion around how to make Drupal more accessible.
Accessibility Wins Tumblr
A showcase of accessibility user interfaces and tools.
A complete guide to web accessibility for developers by Luke McGrath.
The official Web Content Accessibility Guidelines
A complete guide to Accessible Rich Internet Application development.