What does §508 require?

§508 requirements are basically the same as the Web Content Accessibility Guidelines or WCAG from the W3C's Website Accessibility Initiative (WAI)
(http://www.w3.org/TR/WAI-WEBCONTENT/full-checklist.html

The complete Checklist is available at http://www.webaim.org/standards/508/checklist )

You might also want to look at http://www.jimthatcher.com/sidebyside.htm for a comparison between the two sets of requirements