Claire Elise Johnson explores lines, zigzags and folds with her jewellery, which includes these pieces from her origami series. You can check out more from this UK jeweller on her blog, as well.
Bonus link: for straight lines only, check out this stainless steel ring by Massachusetts metalsmith Dana DiPlacido, aka Recluse Designs. Also check out her gallery of leather goods.
Even more jewellery: