Cassandra Claire has written very amusing "secret diaries" of the Fellowship of the Ring characters.
Be warned, they're slashy, though very funny. Don't take them seriously, and start at the bottom to get all the references.
Spotted on Dave's blog, though Cassandra's Harry Potter fanfic is a recent favorite of mine. I'm still not done with Draco Sinister, though I'm going slowly and savoring it, because I know that she's not done with the follow-up, Draco Veritas, yet.