These keyboards are awesome.
http://www.dansdata.com/ibmkeyboard.htm
http://www.preater.com/modelm/
If you ever see a bunch of them being tossed out as surplus, pick them up. They can be sold $20 apiece on Ebay easily. Shipping is quite easy via USPS Priority Mail: Simply take two of the long type flat rate boxes, and insert one into the other. Surround the keyboard with peanuts and it’s good to go! Use any keyboards which are physically broken or missing lots of keys as donors for key caps, key blocks and controller boards. The spring mechanism itself is difficult to replace properly so don’t sell any keyboards with stuck or mushy springs, use them as parts donors.
They clean up with laundry detergent and a rag. Do not simply put in the dishwasher unless you open it up and allow to completely rinse and dry the controller board. The buyer can be responsible for this.
If they have AT cords, AT-PS2 adapters can be had for $1-2 (http://www.sfcable.com/catalog/wholesalecables/30D5-4A.html) or the buyer can purchase his own PS2 cable (http://pckeyboards.stores.yahoo.net/cabdetmin.html) You could also make your own cord, the weird connector is a SDL “Shielded Data Link” jack and is available at Mouser and friends.
Some Pentium 4 and faster systems require resistors to be added to the data and clock lines: http://www.geocities.com/jszybowski/keyboard/
Unicomp provides warranted repair services: http://www.pckeyboard.com/repair.html and also sells newly manufactured buckling spring keyboards: http://www.pckeyboard.com/
Clickykeyboards sells new old-stock Model M keyboards: http://www.clickykeyboards.com/