Is there an easy way (or is there anything I can buy) to trace a dead circuit?

I moved into a 100 year old house a few months ago and have been working diligently on a number of projects, but I've been sitting on some of the electrical projects because I'm not quite sure how to get power to a number of dead circuits around the house.

The house used to have knob and tube wiring, but all of that wiring has either been cut or removed. Romex has been run throughout the house and either run to the existing outlets to replace the knob and tube or the old knob and tube outlets have been left dead and a new outlet with Romex was installed nearby.

My problem is that a number of the Romex outlets and/or junction boxes also have no power. Is there any way I can trace those circuits to see where they go so I can connect them to the breaker box?

I bought a circuit tracer, but that only helps me find which breaker a circuit comes out of, and also only works if I have power to the circuit.

Any help is appreciated!