Apple Accessibility - Useful to Everyone Right From the Start
Apple provides accessibility features, demos and tutorials around to vision, hearing, literacy and learning, physical and mobility.

Apple also provides specific .pdf documents around Accessiblity and the iPad in the areas of Hearing, Vision and Physical and Motor Skills.

Video by @_luisfperez around Apple's iOS 6 Guided Access

SMART Technologies Accessibility Profile
Profile documents how SMART solutions offer visual, auditory, physical and mobility and social and communication supports to contribute to academic and social participation for ALL students. Really impressed with SMART Technologies for promoting a supports versus a disabilities model.

Windows : Accessibility Enables People
Accessibility enables people of all abilities to realize their full potential. Microsoft creates technology that is accessible to people around the world—of all ages and abilities. Site has accessibility features, demos and tutorials for Windows 7, Internet Explorer 9, Office 2010.

Review of Android's Accessibility

Microsoft's Accessibility Blog
Their Twitter handle is @MSFTEnable

Clear Print Guide from CNIB