Worlds and Towns: Useful links by Gurra
There is a lot to learn about CAW, creating worlds, and worlds in general. Some of it can be found here at Simlogical, but not all of it. This is a thread with a few links to guide you in the right direction. 
The Create a World Tool (CAW) is required to create your own worlds. It's downloadable for free from TS3.com.
The CAW FAQ, put together by auntielynds, is a huge collection of links to tutorials, resources and lots of information. If there is something you are looking for, always have a look there first!
The CAW Wiki has a few articles on some more advanced CAW stuff, like pre-population.
The CAW Resource Library forum over at TS3CC has some excellent tutorials that you maybe didn't find here.
The Sims 3 Worlds forum forum at CS3 is also host to some useful information.
The World Index is a list of worlds available for download. If you are looking for a world and don't know where to look, go to the World Index. It should have a world for everyone.
a's png2caw program is for converting images into 16-bit pngs, which is the file format for CAW heightmaps.
If you have additional links, or if you know that any of these are no longer available or up to date; just post here.