As posted elsewhere winding resistance is a very important factor in motor performance. Having found (as posted elsewhere) that manufacturers rarely give this data I put together the measurement system in the photo.
1. The 13.5 volt power supply provides current through the winding.
2. The two resistor block on the left provides a 5 ohm dropping resistor to limit the winding current to roughly 2.7 amps (13.5/5=2.7).
3. The four resistor block on the right provides a 250 milli-ohm reference resistance (4 one ohm resistors in parallel).
4. The voltmeter measures the voltage across the reference 250 mohm resistor and then the winding.
5. The ratio of the two voltages allows simple computation of the winding resistance (Vref/Vwind=Rref/Rwind).
The resistors came from Radio Shack.

I use mostly suppo motors and have measured widing resistances on three of them. Two were measured within several percent of the published values but the third was obviously a suppo misprint.

Now why do I go to this trouble.:
Knowing the winding resistance allows a good determination of the most efficient current to run the motor at.
Just like the 70% kv rule of thumb I find that if winding voltage drop is about 25% of applied violtage that leaves about 75% for the prop. This ratio is usually a good starting point for operation.

I would be interested in how others do this or if they think it is relevant.

The windings are wound as Y or "delta". Externally you can only measure the resistance between any single pair of motor leads or basically one winding. There are three measurements corresponding to the three winding resistances.
Ideally all three measurements should be the same. On one of my motors the three values were:
Suppo 2217-9 on 9/18/09, Suppo spec is 95 milli-ohm.
R-Y 97 milli-ohm (R-Y = Red to Yellow lead)
R-B 97
Y-B 96

This is very consistent for the three windings and matches the Suppo spec very well.
The second purpose of this test is to find shorted out winding turns. Any large difference betweeen winding resistances is suspicious.

I also use this test to see how well the manufacturer wound their motor  - ideally all 3 resistances should be the same.

I crash a lot   so I damage my motors and checking the winding resistance is part of returning them to service.

I measure it on laboratory power supply with current limited to 1A ... the voltmeter shows directly resistace, because 1mV = 1mohm at 1A 

just one smal comment - it is necessary not to measure on the same place as power leads are connected, because if you connect in on the same place, you will measure also junctin resistance and it can show higner numbers than they really are