Developers, designers, programmers. Everyone needs to have an understanding of what making an accessable site. So, it aid in this quest, here many ways of developing for various types types of disabilities.
WebAIM

- WebAIM is a US non-profit organization formed in 1999 that provides resources in designing and developing websites for many different types of dissabilities. Support for HTML, Flash, multimedia projects and assistive technologies are available, as well as classes to gain an even deeper knowledge of accessability and the web

- W3C's Web Accessability Initiative is one of the most exptensive reoursces around. It has guides for Guidelines and Techniques, Planning and Evaluating, Presentations and so much more.

- Another excellent W3C resource. This one shows designers and programmers the difference between sites with well implimented accessability features and poor accessability features. This is a great way to see all of this in action.