WildWeazel
Carthago Creanda Est
The last we were told was "late January or early February." That's already past, so we're just waiting to hear from Firaxis.
The World Builder
Manual: Dale (who turned out to be another one of those elusive beta testers) has made a great World Builder Manual in pdf format.
Manual (7.1 mb)
The World Builder
The World Builder (WB) is the part of Civ4 that is used to create new maps and scenarios. It can be loaded at any time during the game. Many people find the WB slow and clucnky, but fortunately there are other ways to edit the saves. An interesting thing about the World Builder Saves is that they are saved in ordinary text format. You can open, edit, and save them using the most powerful computer program known to man- NOTEPAD. The file is easy to understand, and for small changes it's probably easier to tweak the text rather than loading it in the World Builder. There is also a converter that creates maps from a series of bmp images.
Manual: Dale (who turned out to be another one of those elusive beta testers) has made a great World Builder Manual in pdf format.
Manual (7.1 mb)
Making Maps: There are 3 ways to build new maps. You can use the WB to make it in-game, you can manually set it up in Notepad, or you can use the BMP to WBS converter to generate maps using bmp images.
The World Builder Save (WBS): Dale is also working on a complete guide to editing the WBS in text format in this thread.
Unlock the full capabilities: If you have tried to use the World Builder, you have probably noticed that a lot of the functions have been disabled. This is to keep the World Builder from being a cheat machine, but you can't make good scenarios. Fortunately, Soren Johnson released the "cheat code": In the main ini file, which can be accesed through "Shortcut to _Civ4Config" in the main Civilization 4 folder, replace the line "CheatCode = 0" with "CheatCode = chipotle". This will unlock all the features of the World Builder, allowing complete scenario control.