Sansûkh is an incredibly well-researched, detailed, well-written Lord of the Rings fanfiction, telling the whole story from the perspective of the dead dwarves keeping watch over their relatives. Its protagonist is Thorin Oakenshield, and in addition to all the plots told by the primary books, it also features Erebor and Mirkwood. The writing is very appropriate and well-done, and I enjoyed every part of it tremendously. It’s funny, and it’s epic, and it’s very much as it should be.
Additionally, there are a ton (>300) of adorable artworks, an audiobook of good production quality, the beginnings of a graphical novel, and a SOUNDTRACK, including sheet music. The soundtrack is linked in the appropriate sections of the story, and it’s amazing. This page lists sub-pages which link to all the additional content.
If you want more fanfics in this general direction (though none as good), look at determamfidd’s recommendation document.