This is the hexcrawl ruleset that I've been basing a lot of my game rules on. Specifically I use it as a reference for it's Travel and Navigation rules, The Exploring Day, Resources, and Weather. I really like how it handles weather and have actually created my own weather tables that vary by season for the campaign setting I've got.
The vibe I'm going for is a hunter-gatherer/mythic setting, so lots of strange magical phenomena, ecology, wilderness survival stuff. I'm using this along with restricting long rests during travel to provide a sense of attrition.