The folk at One Page Rules have released a new edition of GrimDark Future, a set of one-page rules (with lots of pages of armies you can also download)
The Barons of Fyn Card and Tile Game
The Barons of Fyn is a free downloadable card and tile game from Bones Games. In the game, rival barons try to expand their borders, building a fiefdom of loyal towns and cities, and strengthening their armies. It’s beer and pretzels for 2 to 6 players. I’ve played this, and its fun.
Generic Easy Miniatures Rules
Shawn Garbett has written GEM — the Generic Easy Miniatures Rules — which seem to be aimed at larget miniatures in a skirmish scenario. Garbett writes:
GEM is specifically for those who are sick of having new revisions of their favorite rule system leave out those great new miniatures they just finished painting. If all the commercial miniature systems have flaws which you really don’t like, then GEM may be just what you’ve been looking for. If you’ve ever been bogged down in rolling and rolling with no resolution in sight, GEM is probably for you. Several other play options exist, for customization to a gaming groups own tastes.
D20 Reference Documents
The downloadable D20 system reference documents provide most of what you need to play any of the d20 system games that stem from the original Dungeons and Dragons system.
Afternova Print and Play Game
Afternova is a free print-and-play game about collecting resources from a solar system after it has been destroyed by a supernova.