I have just about decided that if/when I run my Middle Earth D&D game, it will be set on the borders of Mordor. The Gondorian watch-tower of Cirith Ungol has been abandoned (~1640 TA) after a plague has desolated the region. Now a daring trader named Murlann has setup a temporary camp in the abandoned tower and his small retinue of men provide shelter and goods & services to those adventurous souls that wish to plunder the evil lands beyond the pass.
I plan to use the keep from AD&D module UK3 The Gauntlet as my stand in for the Tower of Cirith Ungol (I love that map). Not that the floor plan will be needed much, as it is my home base for the game.
Of course there is also Shelob to worry about as you explore the pass and the tunnels found nearby...
"But still she was there, who was there before Sauron, and before the first stone of Barad-dûr; and she served none but herself, drinking the blood of Elves and Men, bloated and grown fat with endless brooding on her feasts, weaving webs of shadow; for all living things were her food, and her vomit darkness."
—The Two Towers
One of my initial stumbling blocks to trying to run D&D in Middle Earth was the absence of enough monsters to make it interesting. But after talking to a couple of folks in my G+ circles, I came to realize the answer was in "The Hobbit". Gollum was a hobbit that was exposed to an evil ring for years, and it twisted him into a "monster". Well surely the land of Mordor is just bubbling with "evil" power - so naturally it would twist any natural creatures that lived there. So there, instant "monster" generation - I can now run dungeons full of strange "one-off" monster types. It is my Middle Earth anyway, so canon be damned, it is full D&D ahead.