A separate programming track has been a long-overdue project since switching to DCC. Before, every time I wanted to do something as simple as address a new decoder, I had to remove every other locomotive from the layout. Needless to say, that's kind of a pain.
This was a very simple project. I took the wires leading from my DCC system to the layout and routed them to a DPDT switch. I then ran one set of wire back to the layout and the other to the programming track. Not only can I switch between the two easily, but I can kill the power to the layout quickly if I have to.
The track itself is nothing more than two pieces of Kato Unitrack that came with my Broadway Limited set.