Lamentations of the Flame Princess is an old school RPG of “fantasy adventure and horror.” The link is to the free version without illustrations. The illustrated version apparently has some rather adult and disturbing illustrations.
BioSyndrome is a community created game of zombie survival horror.
Dark Coast is a new fantasy RPG with some unique mechanisms.
Machinations is a simple steampunk RPG. From the author’s description:
Welcome to the Eternal City, the home of the Machinations RPG. Take on the role of an Adventurer, an Alchemist, an Artificer or even a deathless Automaton. Band together with others to form a Free Company and then hire yourselves out to perform acts of sabotage, espionage, assassination, extortion, blackmail or plain old robbery. All in a world a short step from our own, where reason has been lost, empires exist to be built and strange technology dominates all walks of life. It is a world of sinister intrigue, awful power, terrible events and dark portents. There is also beer, song and glory
The World Of Gainar is a massive work — a complete RPG system set in a post-apocalypse fantasy world. This is no Gamma World, however. From my reading, it seems to be more of a traditional fantasy — with dwarves and elves (fey), swords and shields, but also with gunpowder and steam tech. For those who just want the background, there’s a stripped down version that’s just the world book.