Among the business class laptops, ThinkPads have the best keyboards. Even with the change to island style keyboards, I would say that ThinkPad keyboards still beat all its laptop competitors hands down in the keyboard department. Unlike others, ThinkPad keyboard keys are curved to fit your fingers, they have roughly the same surface area as a desktop full-size keyboard and well spaced so you wouldn't miss a key or have to reach far to get to one.
ThinkPad laptops are well built. However, they are also very expensive, compared to competitors with the same spec. So what do you do if you only like the keyboards? You either buy the official USB or Bluetooth Lenovo ThinkPad keyboards with TrackPoint or make your own adapter for the keyboard that you hold dear.
In this Instructable, I will show you the general steps I took to make a USB adapter for the T60 keyboard and its compatible keyboards, ie. if your keyboard shares the same receptacle as the T60. See step 1.
Let's get started!
UPDATE: A kit with all the components required (excluding Arduino) is now available at https://www.tindie.com/products/rampadc/arduino-thinkpad-usb-keyboard-adapter/
Step 1: Get your receptacle
Before diving into the easier part, ie. programming and designing the adapter board, you need to find a way to connect your keyboard to the PCB.
Most classic ThinkPad keyboards use board to board connectors. According to eBay, if you search for T60 keyboards, you will find that ThinkPad T60, T60p, Z61p, Z61t, Z60, T61, R400, R500, T400, T500, X41... shares the same keyboard and their keyboard matrix may also be interchangeable.
From ThinkPad T60's schematics that floats around on the internet (see picture), I found that the T60 uses JAE AA01B-S040VA1-R3000. There aren't a lot of vendors who sell these as they are proprietary. Most of those who do sell, sell with minimum order quantity of 100. At about $4.90 each plus shipping, it's awfully expensive. So if you're interested in getting some of those, message me.
For more information regarding ThinkPad T60 receptacle, have a look at Felix's photos and measurements: http://electronics.stackexchange.com/questions/64112/how-to-find-socket-for-keyboard-connector