off-left
what readers do & don't see

This company produces JAWS and other accessibility products

compare screen magnifiers
Street recommends OPAL

American council of the blind

check list

http://www.marcozehe.de/2008/02/29/easy-aria-tip-1-using-aria-required/
http://www.marcozehe.de/2008/03/23/easy-aria-tip-2-aria-labelledby-and-aria-describedby/
http://www.marcozehe.de/2008/07/16/easy-aria-tip-3-aria-invalid-and-role-alert/
http://www.marcozehe.de/2009/10/31/easy-aria-tip-4-landmarks/
http://www.marcozehe.de/2010/02/10/easy-aria-tip-5-aria-expanded-and-aria-controls/

Very nice and informative FAQ on testing webpages in screen readers. Note the 2nd from last question in this FAQ.