Randy,
Hello. I am an exhibit graphic designer in the exhibits division at the Denver Museum of Natural History. A few years back our museum created an exhibit called Edge of the Wild which was created to be handicapped accessible, along with being visitor friendly to all. 
It was successful as far as accessibility and because of this won the American Association of Museums Accessiblity Award in 1994. So in answer to your question, yes we are interested in improving our exhibits to be accessible to the handicapped. Currently, we are looking into producing a brochure about the accessibility of the exhibits and museum in general, for our handicapped audience. I am a member of a team that is working on this brochure. Perhaps if you have anything as far as a prototype brochure that you would be willing to share with us, or any other information, we would be very grateful. We can give you some insights on what we have learned so far with the "Edge of the Wild" exhibit. I am understanding that you are looking toward the future on creating a directory of sorts. You may also want to contact someone in our marketing department also for some insights on these issues or on the web access. Thank you for your e-mail. It's great  to know that someone has already begun to look at these concerns here in Colorado. I'll look forward to hearing from you. Thanks. Salle Tulchin, Denver Museum of Natural History. My phone @ the museum # is 303-370-8283.