Lots of wonderful stuff to get your teeth into in The Inclusive Design Guide:

The Inclusive Design Guide can be applied to digital design as well as to the design of services, the built environment and physical products. It can be applied to processes like workshops, meetings, conferences, and even our daily interactions with one another. It can be used by anyone.

By the way, I found this via an excellent collection of accessible design resources put together by Chris Nasrawi.