phranque - 9:02 am on Sep 16, 2010 (gmt 0)

you might want to try the Firefox Accessibility Extension.

one of the best tools for accessibility testing is Lynx, which is a text-only browser - no images, no javascript, no style, no mouse.
if your site is usable in lynx you're probably ok with screen readers, etc.
it won't hurt your SEO for that matter.