I've always thought the single most important thing is to MINIMIZE THE NEED FOR MOUSE USE. This relates not only to blind people and those with arthritis and so on, but also to the able-bodied who are trying to minimize repetitive strain injury, or keyboard-oriented people like me who just don't like using the mouse more than is absolutely necessary.
Thus I have always tried to design my site so that it can be navigated easily without a mouse if necessary.
This is among several reasons why I never use frames or drop-down menus or java scripts, among other things.
It is a great pity that so many people, when they learn to use a computer, are never told that most of the things you can do with a mouse can also be done on the keyboard. Training courses for software programs tend, in my experience, to perpetuate this problem because the trainers only ever tell you the mouse way of doing things.
