Chris Goodwin has been working on a retroclone of Metagaming's old In The Labyrinth RPG system. He has a playtest version ready for people to look at and comment on:
My retro clone game, Warrior & Wizard, has reached what I consider minimally complete for playtesting. There are rules for creating characters, fighting using magic or weapons, and building them up through experience. There's also a minimal bestiary containing every type of creature capable of being summoned by the included spells, plus a few extra (stats may or may not match those in the original game). There's an experience point section that doesn't match the original game.You can find the playtest draft on Google Docs here and comment on this playtest version in this thread on the RetroRoleplaying Forum.
There's not any rigorous setting building information, and information on noncombat Skill use is a little light aside from what is provided in the description of the Skills themselves.