I am thinking about building a current fold back for a USB power cube. But first I need to be able to measure the current. A LM324 can do this quite well:

Figure 1​

I'm not so sure about this layout:

figure 2​

it is almost 11:00PM my time and I am fried. I'm done for the night. Thoughts, suggestions?

 

How will the output of the leftmost opamp swing below ground?

 

A LM324 can do this quite well:

Actually that should be -1V = 1A, and to achieve that you would need a negative supply.
I'd also dispute "quite well" when referring to an LM324! An LM324 can't do anything quite well. Offset voltage will become a problem when measuring small currents.
I'd suggest a shunt amplifier such as INA181 or AD8418.
This would work if you want to use an op-amp in inverting mode, provided that the common-mode input voltage includes the negative supply (which it does for an LM324) R1 is the load resistor.

 

Now there are IC devices made for exactly that application, boosting the voltage from a shunt. One of them would be a better choice. Not as cheap, though.

 

One of them would be a better choice. Not as cheap, though.

INA180 = 60p each, worth every penny! It does save four resistors, which is probably only a saving in placement costs.

 

INA250A4 is a better, if slightly more expensive (£2.90) solution with internal sense resistor, gives 2v per amp output.