Well, I'm not sure how many people are into the Silmarillion section, but I've found that that's where one tends to find the jewels of Tolkien fanfiction.

Discovered Through the Darkness Unescapable by chryseis dione the other day. It is the tale of the Alkallabeth (fall of Numenor, similar to Atlantis) through the eyes of Tar-Miriel, the last queen. It is heartbreaking and gorgeous and it has definitely sucked me in. Check it out!