FasTap Keyboard for Mobile Phones
Here is an innovative concept for a small keyboard that can be operated with one finger and it is on a cell phone. One of the best features is the software algorithym that assumes you don't want a number in the middle of your word and will ignore it. These kind of concepts could be applied to adaptive equipment.
Gearlog : FasTap Keyboard for Mobile Phones
CD Switch-Kit
RJ Cooper has a fun little project to make your own switches for various devices. Since large switches can get pretty expensive, this method to make one for $10 looks pretty interesting. I've built quite a few varied switches using door bell switches and others from Radio Shack and this one looks very workable and has its own charm.
I would be interested in hearing from someone who uses them how well they work and if they wear out. They look like they aren't for a very light touch but could take some abuse. There's a video on this page that shows a bit how they are put together.
Assistive Technology - Switch-Kit CD Switch