What basically happens with resonance is that you insert a tiny bit of energy in a circuit at given times (resonance frequency) and because of the properties of the circuit this tiny amount of energy has nowhere to go other than swinging up an down from capacitor to inductor.
What happens if you keep supplying this tiny amount of energy is that the total amount of energy in inductor and capacitor builds up and as a result the voltage and current in the circuit increase until an equilibrium is reached. At that point the load resistor (or your oscilloscope, or multimeter, or ... ) drains just as much energy from the circuit as is being fed.
This means: For a parallel circuit you want a alternating voltage source with a high impedance (or even better a current source), so you feed a tiny amount of energy into the circuit and at the same time the source doesn't load the resonant circuit too much so it will build up energy. The same goes for your meter, you want a device with a high impedance to check for resonance, otherwise the meter will drain too much energy from the circuit to measure the resonance.
The same goes for a series circuit but with low series impedances and a low impedance voltage source. The 100 ohm resistor and the speaker will dampen the circuit too much to notice too much of the resonance. The easiest way to prove resonance in this circuit is to use a voltage generator which you can vary the frequency of. That way, despite the load resistors, you should be able to hear the volume change with changing frequency. Do remember though that your speaker will have a certain volume/frequency response too (probably including resonance frequencies of its own).