A good keyboard is worth as much as a good monitor: because you should be spending the most on the part of the computer you actually touch. Computers have now been flooded with lackluster rubber domes, but gaming enthusiasts have revived the concept of the the premium Mechanical Keyboard.
- IBM Buckling Spring Keyboard
- IBM Wheelwriter - The IBM Wheelwriter surprisingly is equipped with a buckling spring keyboard, the same switches as the Model M. In fact, it can be set up to work on a modern computer with a keyboard controller.
If you're making or repurposing an old keyboard, you will need a keyboard controller to convert those electrical signals to USB input. Also, if you need a keycode converter (PS/2 to USB or AT to USB), a converter is what you need.
The Teensy microcontrollers with Atmel chips work great for this purpose. Also Arduino Micro for small keyboards/converters on the cheap.