I've added support for generating ring and bracelet loops to LinkRez, whose release is still probably a week or two away, pending my ability to write decent documentation, and forcing myself to stop adding features.
It seems like a lot of people like to release jewelry in sets, including sets with necklaces, bracelets, rings, and earrings. I can't do much about earrings, but bracelets and rings are intrinsically "loop"-like, and I figured it'd be nice to be able to use the same links, commands, and notecard programs to generate bracelets and rings.
If you really look closely at how necklace links "rotate" from the front of the torso to the back of the neck, you'll realize that there's generally a 90 degree rotation around the axis of the necklace path, from the front to the back of a necklace. Bracelets and rings (and skirts...) are all simpler in rotational structure than necklaces, without this "twisting."
with bracelet mode, using an alternating angle linktype
Also, TINY links can be placed to make loops that are ring sized. Starting with a severely dimpled sphere, converted to a tapered cylinder, and with a gemstone texture applied, I generated a tiny "sapphire," and ran it on the sizing board. Notice how far above the gem the perceived "center point" is -- this is NOT a prim that could be placed in a useful shape with LoopRez. Incidentally, the diameter of the gem is 1.8 mm -- really tiny!
Loading the gem into LinkRez, along with some similarly sized gems with random colors just for fun, I was able to generate this rather awful looking ring. This ring is actually about twice the minimum size possible, so you could get even smaller loops.
So, you can now easily make rings with any assortment of severely tortured prims. For example, maybe one made up of a large central stone, flanked by some spacing elements, flanked by some tinier gemstones, followed by an incrementally twisting set of connection links. I think it could be rather poweful, in the hands of a real jeweler.
Lastly, I played with some tiny tubes, per Natalia's excellent tiny prim jewelry tutorial, and make a necklace with it. I'm still rather enamored of how nicely the prims are aligned.