Here's what I've been messing with this week, our old wooden above ground veggie bed collapsed awhile back, so I decided to sift the rocks out of the dirt and use the rocks in the driveway. 
I've got close to half the rocks out so far, 3 wheel barrow loads. 
  
 
  
The sifter is made from 1/4 inch Hardware Cloth on a 2x4 frame