Dirk's (Dubz) article is a good summary of material relating mostly to the 18th century and later, and does a great job of dispelling the myth of left-hand laid rope in common use.
I can add from my background in maritime archaeology that I have never seen left-hand laid rope on a shipwreck, but all of the cable I have seen is left-hand laid. We are right now in the process of publishing a major book on all of the rigging finrs from Vasa (sank 1628), which includes over 500 yards of cordage of all types, from spunyarn up to anchor cable. A brief summary of how the Swedish navy rigged their ships based on this is the follows:
cables and mooring lines: cable-laid from nine strands, left hand
Shrouds: a mixture of three-stranded and four-stranded rope, right hand (four strand with a heart), no worming or serving
Lanyards: three strands, right hand
Running rigging: mostly three strands, right hand, but lower halliard ties and topsail sheets are four strands with a heart, right hand
Gun breechings: four strands with heart, right hand, served (some are reused old rope, possibly old shrouds, most are new)
Gun tackles: three strands, right hand.
An important point is that in the making of rope, each stage of the process twists the material in the opposite direction of the previous stage. Almost all yarn for rope is spun from the raw fibre as right-hand twist (Z twist), both in the ancient world, when yarn was spun by hand, and after mechanical spinning wheels were introduced. This is different from how yarn or thread for making cloth is made, where both left and right twist can be used, and many fabrics are made with the warp twisted one way and the weft threads the other.
After spinning of the yarn, the yarns are laid into strands (left-hand), and the strands are closed into a rope (right-hand). A cable adds a further stage, laying three ropes together left-handed. The reversing of the twist is necessary to balance the stresses in the rope so that it will hold together in use. If properly laid, so that all the twists are balanced, the rope is said to be dead, and will not twist or kink when loaded.
Fred