There is a new Google search announced yesterday that will try to give higher rankings to pages that accommodate blind and visually impaired users.
http://labs.google.com/accessible/
It’s supposed to give higher rankings to pages that are simple and easily navigable by keyboard and comply with W3C guidelines. A quick look did not impress me - the sites that ranked well were not particularly good but not really spam either. I saw a high percentage of junk results like bizrate, craigslist and alibaba and the like. Odd that it doesn’t seem to care much about 508 compliancy either.