1) POTR/LOTR Crossover. I have the phrase "Captain Jack Sparrow of Umbar" wandering around in my head. Bonus points if you set it during the time of Thorongil, and his first victory over the corsairs.
2) There are few opportunities for IC femslash, but one possible pairing has invaded my brain: Nerdanel/Amarie. Both lost their significant other due to the flight of the Noldor, although it is true that Nerdanel had possibly kicked Feanor out to sleep on the couch a while back. Somebody write this for me?
3) Thorongil/Théoden slash. For that matter, any stories about Aragorn's time serving under Thengel. I've seen lots about him while he worked for Ecthelion. But why did he go to Rohan first? Just to prove himself? Because they had a good pension plan? WHY?