Well, there's Apocalypse World. There's a second edition coming soon, but you still check out the first edition to start learning it.
Thanks for the info....is this the same group that's doing Dungeon World?
No. Dungeon World was a hack of Apocalypse World. Apocalypse World is the game that Dungeon World got it's rules from. The core mechanices (roll 2d6, get a 10+ or 7-9) are the same, but the game plays very, very differently.
Vincent Baker wrote Apocolypse World and it was released with either an OGL, CC or similar type license. He's also the author of Dogs in the Vineyard.
The good thing about AW is that it lends itself to short campaign arcs and require virtually no planning on the GM's part. In fact, planning is actively discouraged in the game. The down side, is it doesn't do epic, long campaigns well and the mechanics will actively fight you if you try to have a plan.
With a single set of characters, the game can play really well out to about 12 sessions (or about 40-50 hours of game play). After that, you'll either want to start retiring characters and bringing in new ones, or wrap up the story.
There is some resource management in the game, scarcity and even lack of certain things, but it focuses more on the brutality surrounding those scarcities. Think of the Mad Max movies for example. The resources of gas and water are rare, but often as not, the real story is about how people act around those rare resources.
Recently I was a player in a post apocalyptic game we used the True20 system by Green Ronin. It was set in modern day and the apocalypse event happened in our first session.
