Making Ajax Work with Screen Readers - Perhaps the single most enlightening current article that helps us understand the difficulties with AJAX ... This article is a must read for anyone who is really interested in why all the current fuss about AJAX accessibility. Bottom line, screen readers are not yet capable of reliably recognizing when dynamically updated content has changed...AJAX and Screenreaders: When Can it Work? - [author James Edwards] has invested a tremendous amount of hard work understanding how JavaScript and screen readers interact. His tests and results are posted right here on this blog. James investigates at a level of detail that would try the patience of most. His SitePoint article explores an how various approaches work and fail (too often) with a dizzying selection of screen readers...
AJAX Accessibility Overview - ... Becky [Gibson] offers a number of very reasonable ideas which improve the likelihood that the material will be discovered and handled by screen readers. Such as: Place dynamically updated material after the trigger event, later in the reading order. Write new material into an existing div instead of creating a new one...
In closing, the article mentions that a number of people including the authors of the above three pieces are working on longer term solutions.