One of the side-projects I've been poking at for over 8 years now is a fantasy version of Traveller: back in 2008, the moderator over at the odd74 (Original D&D) discussion board posted a picture of a non-existant game called "Wanderer" (
http://dirk.files.wordpress.com/2007/07/dsc01828.jpg ), and several people have been developing their own version.
I've been doing mine as in intellectual exercise of "What would Marc and Loren and Frank have done if they made a fantasy game instead?" and have been butting my head against several roadblocks: sailing ship design, world design, and the economic system. The problem is that everything in Traveller is so well integrated and interconnected, so it is hard to work on one part without needing to consider every other part as well.
The first book - Characters and Combat - is mostly done (except for prices), and I have put in some work on the other two books. Perhaps sometime in the foreseeable future I'll have enough of the other two do do some playtesting...assuming I find both players AND time. (As the main character in Dork Tower laments: "God doesn't play dice with the universe. He plays a resource management Eurogame I suck at")
At the moment, the project is fighting for time with one of my OTHER projects: adapting the Terran Trade Authority background to the (mostly-CT) Traveller rules.