I love the original IBM Type-M buckling-spring keyboard. No other keyboard gives the same tactile feedback. My co-workers are audibly aware of my preference. I've managed to save several PS/2 keyboards but eventually they wear out. Looking for replacements, I found:
* [PC Keyboard](http://www.pckeyboard.com), nee Unicomp, sells
keyboards based on the buckling spring design that IBM/Lexmark used to
make. I'm intrigued by their ‘Linux 101’ unit with the Control and
CapsLock mapped correctly. $100 direct.
* The [Tactile Pro Keyboard](http://www.matias.ca/tactilepro/) from Matias, a usb keyboard for Mac or PC, is highly regarded. $100 direct but [Smalldog](http://www.smalldog.com) has them for $80.
* The Avant Prime, similar to the Northgate Omni, can be had for $149 from [Lueck Data Systems](http://www.lueckdatasystems.com/en-us/hardware/keyboards/).