30 Rails is a free print-and-play roll-and-write game played on a 6×6 grid. Players draw mountains a mine and stations and then fill in the remainder of the grid with track based on the outcome of die rolls.
Dungeoneering dot Net has a nice selection of printable terrain tiles ostensibly for use with the Dungeons and Dragons miniatures game, but which would also work with any number of dungeon crawl games — of which there are many free ones available on this site.
Cheapass Games offers Renfield, a card game about parts, tools, gravestones and “yummy delicious bugs.”
Unbound: Endless War is a free print and play game for two p layers in which you build a map and attempt to take over a players’ bases. It’s a pay-what-you-like game.