Hello,
I've used breadboards and from what I understand they are "bused" (the holes are connected vertically/horizontally).
I have an XBee shield with a prototyping area, but I don't understand how to use it. They don't seem like they are bused. Am I missing something (or some tool, etc.)?
Well, there is no real difference between the Xbee shield and many other "proto" shields.
These are essentially "protoboards" rather than "breadboards", the difference being that they are designed to put as much as possible into the given area. Breadboards are extremely inefficient in their use of the available space as you have five points for every connection and more power "bus" points than you will ever use on one project.
Obviously with a "protoboard" you have to solder components, so you solder as many connections to the projecting wires or pins underneath, as you require. It is for a more permanent application. You can of course, get a little breadboard to fit over the "proto" area in many shields.