For users in your organization with disability issues, Macs offer built-in accessibility features. Check out the Universal Access options.
MacWorld's Christopher Breen made an excellent video that highlights the Universal Access options on Macs and offers tips about how to use it -- including some features that may be useful to everyone -- not just users with disabilities.
Very few Mac users understand just how powerful Universal Access is-or what a bargain it is. For the last several iterations of Mac OS X, Apple has included the kind of accessibility features that, on Windows, you had to pay a small fortune for. Universal Access is one of those features that demonstrates just how focused Apple can be on all of its users.
The video can be viewed by following the link above or watching it as embedded below: