The Hastur's Workshop Archive
Hastur's Workshop, at Double Aught's site, has long been a source of inspiration and answers for marathon mapmakers intent on a better product. Michael Watson decided to preserve those pages in an offline form, in case they are ever removed from Double Aught's pages. (I think as an offline source of mapmaking tips, they're useful enough as they are, no need to justify them as historical.) Comes with a bonus Bungie Forge/Anvil FAQ v2.0.