First up, via Alhambra Investments:
And from SmallCapInvestor (please note, none of these companies are actually producing REE's yet):
***Molycorp (NYSE: MCP) has been one of the more discussed names recently. The company just went public via an IPO on the NYSE. With its location in Mountain Pass, California, it's one of the few U.S. based companies that is publicly traded. Molycorp's deposits tend to be of the lighter rare earths.
Avalon Rare Metals (OTC: AVARF.PK) is located in Toronto, Ontario and has deposits of some of the rarer, heavy elements. Located in remote northern Canada, the Nechalacho deposit is hard to get to, and very expensive to mine.
Rare Element Resources (AMEX: REE) also has light rare earth deposits, but with some dysprosium has exposure to the heavier elements as well. Located in Vancouver, British Colombia, Rare Element is an exploration stage company with its major property in northeast Wyoming.
Great Western Minerals (OTC: GWMGF.PK) is a tiny $80 million market cap exploration company located in Saskatoon, Saskatchewan. Its alloys are used in the magnet, aerospace, and battery industries.