The current episode of Freedom Scientific’s podcast called FSCast has an extensive discussion of ARIA (accessible rich internet applications). At a high level, ARIA is a way to ensure that the complexity of desktop applications being reproduced on the web remains accessible.
The podcast is worth a listen for anyone interested in web accessibility. Although JAWS is used in some of the demonstrations, the discussion of ARIA hits at the benefits and challenges of ARIA for any screen reading user. Take a listen to the podcast directly at http://podcast.freedomscientific.com/FSCast/episodes/fscast026-january2009.mp3.