Here's a bit about Andvarinaut, the cursed ring from Norse myth, and the likeliest source of inspiration for Tolkien's One Ring:
In Norse mythology, Andvari is a dwarf who can assume the shape of a fish if he is pursued. He lives underneath a waterfall and collects great wealth with the help of his ring, Andvaranaut.
He was caught by Loki with a net provided by the goddess Ran and forced the yield all the gold he possessed. The dwarf tried to withhold his ring so that he could rebuild his wealth. Loki made him give up the ring as well and the dwarf cursed the stolen gold which would from then on bring disaster to all who owned it.
The gold was used by the gods to pay a blood-debt to pay Hreidmar, the father of Fafnir, because they had killed his son Otter. This myth formed in later times the prelude to the Nibelungsaga.
Wagner told the story of the ring in his famous operatic cycle Der Ring des Nibelungen, which charts the progression of the ring from Andvari to the end, showing the endless stream of misfortunes that befalls those who hold the beautiful ring.
Some have said that andvaranaut is the basis for the modern urban legend about the Hope diamond, which is also beautiful and worth a fortune, but is said to bring pain and misfortune to all who hold it.
-- from Pantheon.org (thanks, Micha!)
And that's about a billion parallels, in case you missed it ;-)