Hi Susan,
Your question about cultural accessibility and Web design is an excellent one! I'm glad you asked.
The Antima Group has some
free PDF case studies about cultural influences on Web site interactions. I think their research might be of interest to you, including the PDF on best practices in Web globalization.
The
NIHSeniorHealth.gov site is a good example of a well-designed resource targeted to the senior community. Excellent example of accessibility at it's best. Perhaps this site is not exactly the "cultural" example you're looking for, but it's still a good example of accessibility done right -- in this case, the target "cultural group" being senior citizens.
Notice on the site that particular attention is paid to ease of use, targeted content presented in a simplified layout, and helpful reading aids -- all elements that enhance the visitor experience.
Hope this helps!
Yann