SofType 5 OnScreen Keyboard
SofType is a software utility which replaces the functionality of a desktop keyboard with a full featured, on-screen keyboard. SofType can be accessed using a mouse or mouse emulator such as the HeadMouse Extreme. SofType works by generating an image of a keyboard on the computer screen. When a key is selected (clicked), the character represented by that key is sent to the Windows application with focus.
More information: http://www.boundlessat.com/Mobility/OnScreen-Keyboards-Mice/SofType-OnScreen-Keyboard