If your are using some op-amps from time to time, you can easily make a small regulated power supply with it. I for example am using this circuit on breadboards from time to time when I need some bizarre voltages or if I simply have one amplifier from a quad-opamp-IC left over.
The idea of this circuit is really simple. It only uses one op-amp, two resistors and a NPN-transistor. The only thing you have to keep in mind is that this circuit needs a minimum load of a few mA or less, otherwise the regulation will be inactive. A small LED-indicator for power indication will be more than sufficient.
And so you can better imagine the concept, here is an example for a regulation from 9V to 5V:
The resistors R1 and R2 are functioning as a reference voltage. If you need it a lot more precise ou can also use an actual voltage reference, but I wanted it to keep it simple here.
At the power-on the reference is higher in voltage than the output voltage, so the opamp is turning on the NPN. The voltage is rising until it reaches the reference voltage. From this point on the opamp will try to keep the reference and the output voltage the same, so the regulation is fully working.
This circuit is useful espacially for smaller currents (=< 1A). At higher currents and current fluctuation the circuit might get unstable and connected components might get damaged by higher voltages than usual. You can sort of prevent this by connecting a few µF in capacitance to the output voltage.