What the heck is pV^/Hz ? It is a noise figure, but I'm not sure what it means in the real world.

Does anyone have any information on what this is, how I could measure it on my finished amp, and what I'm looking for for noise figures?

The noise figure is usually expressed in units of pV/sqrt(Hz) (i.e. pico-volts per square-root of Hz), or even more commonly, nV/sqrt(Hz). It could be expressed as pV^2/Hz (this is just the square of the other one), but this has less intrinsic or intuitive meaning.

Basically, you can use this figure to determine how much noise will be present, based on amplifier bandwidth. Ex. if you have 4.5 nV/sqrt(Hz), and a bandwidth of 20 kHz, then you will have 4.5 nV * sqrt(20000) = 636 nV or 0.6 uV of noise. Note that this figure is usually referenced to the input of the amp, so now multiply it by the voltage gain of the amp, say 20 (which is 26 dB gain). Now you have 12 uV of noise at the output of the amp.

But to caculate the noise accurately, you will need to account for noise sources other than the input-referenced voltage noise. These include the input-referenced current noise (input impedance of the amp converts this into voltage noise), resistor self-noise (thermal noise), etc.

I would imagine that you could find some noise application notes or design guides at Analog Devices or TI or Linear Tech that will go into lots of practical detail about noise sources. Take a look.