I had planned my first time travel-related love story, The Stream of Memory, for Nanowrimo 2007 when I first watched the Doctor Who episode "The Girl in the Fireplace" and heard figgylicious talk about The Time Traveller's Wife, both of which deal with the same subject matter: a man who travels through time in love with a woman who cannot accompany him. The premise of my story is still a bit different: if you have read Orson Scott Card's Homecoming series, the woman is quasi-immortal due to an artifact that she carries. I think it makes for a somewhat interesting combination.
ETA, 10:00 CDT Fri 28 Nov 2008 - Never satisfied with my titles, I'm thinking about changing back to Memory and Time. The original inspiration for the story was a line out of Annie Lennox's "Into The West" from the soundtrack to Lord of the Rings: The Return of the King.
I wonder if anyone has ever set time travel in Middle-earth. It wouldn't surprise me, as people have set space travel in Middle-earth before, and I read a fairly good fanfic once where Finrod started raving about dragons being biomechanoids. (If you read the text of The Silmarillion closely, there is some question of whether dragons are living creatures or animated constructs, like the golem of Jewish mythology.
So, how does time travel work in your favorite universe? Is it deterministic? One-way forward? One-way backward? Why do you like it that way?