What is the best way (node) to generate turbulence on particles?

Dependes on your effect but a quick easy way is found in the force node on the noise tab.
You can also use the variance parameters on you PoP source node
and put in some noise with an expression, while this isn't turbulance is it a handy way to add noiseand a bit of variance.

Thanks Lynbo.. I'll try that

lynbo
Dependes on your effect but a quick easy way is found in the force node on the noise tab.

The Noise tool on the Drive Particles shelf does exactly this as well.

Ah cool didn't really realize that was broken out into its own tool as I have gotten used to using this the “Old” Way
I like this even better.