American Stonehenge: Monumental Instructions for the Post-Apocalypse: "Approaching the edifice, it's hard not to think immediately of England's Stonehenge or possibly the ominous monolith from 2001: A Space Odyssey. Built in 1980, these pale gray rocks are quietly awaiting the end of the world as we know it."
These are certainly durable but I don't see how the inscriptions would be of any use in rebuilding civilization. It is also obvious that those "guides" are hard to understand now, if they are hard to understand now, how easy would they be to understand in a post-apocalypse world?
Right now it feels like we are oscillating between a New Golden Age and a New Dark Age. I don't know which we'll choose, for all I know we may end up with oscillating for quite some time; maybe even dampening out to some kind of steady state. This project is to help out in case we choose poorly.
Since I don't know where we'll end up I'll assume we'll have to start at the beginning: gathering wild foods and hunting with found tools.
Then you can start shaping your tools and planting food deliberately and producing fire on demand. You can also make windmills and waterwheels for energy sources. Building a reliable and abundant source of food is the first major step in rebuilding civilization.
Then you can start making charcoal and smelting metals for tools.
With metal tools you have made another major step. Once you can shape metal you can make stoves which make food production much easier. With a little bit of chemistry you can also make refrigeration and engines and finally electricity.
I really think electricity is the best sign of civilization because it is a lot like cash. Cash is good for practically everything and much more efficient then barter. The same goes for electricity. With it you can create light, heat, cold, movement, very complex patterns quickly or repetitively. You can use electricity to convert one thing into practically anything you need, just like cash.