AssistiveWare

Free
KeyStrokes™ is an advanced on-screen keyboard, providing full access to the computer for those with physical impairments and touch screen users.
Free
SwitchXS provides full access to Mac OS X and apps for people with limited mobility, with mouse/keyboard emulation and pre-defined scanning panels.
Free
Transform various text files into speech tracks.
Free
Proloquo is a multilingual speech and communication solution.
Free
VisioVoice includes an advanced document and selection reader.