This page in particular provides scenarios and accessibility solutions for users of web 2.0 who are disabled. It includes information about color blindness, deafness, classroom student with dyslexia, cognitive disabilities, etc.

The Web Accessibility Initiative (WAI) contains a wealth of info about web 2.0 accessibility for those with disabilities. My favorite feature is that it provides scenarios of both children and adults who have disabilities, the barrier that they face, and how to overcome that barrier.