Everett Zufelt (aka @ezufelt) is the Drupal 7 Core accessibility maintainer. He is an assistive technology user himself, and was working with Mike Gifford and Open Concept to help improve the accessibility of Drupal 7.
He also talks about the Common Look and Feel for the Internet 2.0 (CLF 2.0) standards set by Canada for their government sites.
Finally, Zufelt talks about tracking Drupal issues tagged with "Accessibility", as well as how he intends to create a portal page on Drupal.org at http://drupal.org/accessibility with more information on Accessibility. It currently doesn't exist yet, but in the meantime you can check out the Accessibility Group on g.d.o. for more information on Accessibility and Drupal.