Just finished converting a Kenmore 461-95882 5.7 Cu. foot fridge (I got a floor model cheap at Sears). There are a few important details to note about converting it that I wish I'd known ahead of time, but the conversion was pretty straight forward.
First, the top of the fridge is a plastic shell which contains a thermostat board and controller (these are part of the front-mounted temperature display and controls on the exterior of the lid). You can unscrew the top and unplug the wires from the controls easily. There's about a half inch air gap between the lid and the top of the fridge, which is the exterior metal shell. Underneath that is about 2 inches of insulation, and then the plastic inner shell of the fridge. I'm fairly certain that this basic fridge is used as a Kenmore kegerator as well as a fridge, since the interior metal shell has a ~2" circular hole in its center. I drilled out this hole to do my conversion.
Now, the few issues:
1) As far as I can tell, there are no coolant lines running across the top of the fridge. they appear to all be in the back.
2) If you drill the hole in the center, you will hit the wires for the dome light. They're (annoyingly!) buried in the middle of the foam insulation, so I didn't see them when inspecting the fridge. I cut them, but since I disconnected the light switch, it wasn't an issue.
3) The air gap between the outer plastic shell and the top of the metal shell of the fridge itself is significant. You will probably wan't to mount your tower to the metal shell, so cold air doesn't leak.
Other than the lighting wire, it was a pretty straightforward job of converting it to a kegerator. It holds two corny kegs and a 5# C02 tank with some room to spare for bottled beer. It should also hold 1 corny keg + a better bottle fermentor (6 gal), but I haven't tried fermenting in it yet.