With perlin ridges set in the fractal's noise flavour and low, close values for scale, you can make decent looking sand ripples by stretching the X or Z noise, depending which way you want the wind/water to have piled the sand in relation to your FOV.
Here is a
very quick shot at it just while I read this thread, quality isn't a factor here, just demonstration...
[attachimg=#]
Here's the values I've changed in a default power fractal...
scales: Feature=0.5, Lead-in=0.5, smallest=0.25.
Colour: Contrast=1, roughness=0
Displacement: Amplitude=0.25, roughness=0
Noise: Flavour=Ridges, XYZ stretch= X=5, Y=1, Z=1
Warping: Disabled everything here.
The camera is 5m above the surface, these ripples are quite big then.
You can get the idea, though.
I'm looking directly down the Z axis so the X value needs stretched to make the ripples go horizontaly like this.
To make tighter ripples, drop the Z-stretch value, in increments of 0.1 until you have the desired size, is how I'd go about it...