There are many software resources out there that are available for free, which provide access to computers for those with disabilities. (For a great discussion of what's out there and how it's used - or not used- in the educational system, click here.)
My SmartNav stopped working this weekend. Gamers use them for hands free gaming, but I use it to move my cursor and click. Basically, you wear an adhesive dot - on your forehead, eyeglasses, the brim of a hat, your knee, etc. - and direct it at an attached external camera to control the cursor. The device is costly so it's not something I will replace immediately.
But I googled and found a program called Camera Mouse 2009, which is free and will help me out. You do need a webcam to use it, but it's easy to learn.
I was very grateful to find it and would like to pass it along to anyone else who would find such a program useful.