Rob's Dungeon Game is a very basic, retro-style roleplaying system designed for high-fantasy roleplaying. It is not a "retro-clone" - it is a unique system strongly influenced by the Fudge System and by the first generation of roleplaying games (those from the 1970's).
RDG is in draft form. While the rules need a bit more work, playtesting, and fleshing out, the provided material should be enough for any avid dungeon hackers to get started.
License: Open Game License 1.0a
The core rules for the game are available in OpenDocument and PDF formats right here:
Here are some of the [handful of] charts from the core book, such as dice statistics and scale charts. These are the master copies from which those in the core rules are maintained:
And here is a tome of monsters which the PCs can smite. It is of course far from complete, but... isn't everything?