Here's what I thought of - others may (and almost certainly will!) differ and it would be interesting to see some other thoughts. I'm also modifying my definition of source a bit: source is the point where energy becomes available in a useful form (heat, steam, etc.) for producing motion.

* Steam Locomotive
Power Source: the boiler. That's where energy is converted from storage (fuel) to something that can produce motion.
Transmission: the cylinders (steam engine proper) and rods.

* Electric Car
Power Source: the battery. It not only stores the energy, it also produces it in a form that can be immediately used for motion.
Transmission: the electric motor and everything else that gets it to the wheels.

* Electric Locomotive or Streetcar
Power Source: the power plant wherever it is. Electricity comes from the wires ready to produce motion without further conversion.
Transmission: motors and gearing. Should the control systems (transformers etc.) be included? How about the wires themselves?

* Jet airplane
Power Source: the jet turbine engine. Fuel is burned in the engine to produce heat.
Transmission: the engine mounts and exhaust stream (reaction mass).

* Hybrid-electric car or truck or bus (Comment: this beast is too complicated to be a long-term proposition, and only the Japanese have the necessary exemption from Murphy's Law to make it reliable.):
Power source: the engine or a fuel cell, and the battery or other supplemental electric storage. The engine or fuel cell burns fuel to produce heat and motion (or electricity in the case of the fuel cell), and the battery/capacitor supplements that.
Transmission: electric motor(s) and gearbox(es). In some cases, the engine can directly drive the vehicle with electric help (e.g. Prius); in others there's no physical connection and the elctric does the whole thing (e.g. Volt).

* Diesel locomotive
Power Source: by now this should be obvious ... the diesel-generator set. It produces electricity, which powers the ...
Transmission: motors.

* Prop plane
Power Source: the engine(s).
Transmission: the engine mounts and props.

Planes are a little funny. Unlike the others, nothing driving the vehicle is attached to it - all the jet or the prop does is push air. Without the engine mounts, the plane doesn't work. The others carry the engine around, but something in the transmission is attached to the vehicle to transmit forces.

OK. Happy Holidaze and back to the normal railfan stuff.