Being a graphic design student with a neck injury led me to seek out new ways to work that didn't cause me constant headaches. One of the things this search led me to was the Wacom tablet. It's a little flat tablet that you use with a pen tool in lieu of a mouse. You might think it's just better for drawing and doing generally graphic-oriented things, but it's truly superior for all purposes. The first 20 minutes can be a little daunting, but as long as you have it set to pen-mode (where positions on the pad correspond directly to positions on the screen) it's incredibly intuitive. The hand position is natural, the way you would hold a pen, but more relaxed. You can even program it to recognize handwriting.
The pen features customizable buttons. Tapping the pen to the tablet equals clicking, and I have my buttons set to right-click. The tablet itself features 2 buttons and a scrollbar. These buttons are also programmable to any common use you wish. I have mine set to launch a screen-capture application, and the other to the Adobe "Save for Web" command.