Cool little thing I discovered - by peeling the casing back on a 9V battery, one can salvage a clip for connecting other 9V batteries to circuits - sort of like battery clips commercially available. I did this by carefully twisting and rolling the metal case away to reveal the six small batteries inside the larger 9 volt. The little terminal tab at the top popped out, and I was able to solder wires on to the backside, like so:
As you can see, it is just the top of a dismantled 9V battery with wires soldered to the back, but it works quite well for attaching power to circuits.