It is a website dedicated to plastic and glass rings (because the author is allergic to metal), however she does discuss metal rings on her blog and there are so many beautiful and bizarre things on there I don't even know where to begin! I suddenly want so many things that I didn't even know I wanted, or even that they existed at all!
A Runway ring - http://www.nonethericher.com.au/:
Tiny cities on rings by - http://alinek.jimdo.com/les_villes_invisibles.php
Many of the rings are pretty much unwearable for your average person, partly because of price, but partly because many of them are just insane. Insane but wonderful - I'd like to hang them all over my flat. :)