This page used to contain a list of useful tools and materials however this has been pretty much replaced by our glossary, and that is the place to look if you want to know what something is.
If you are about to start making terrain and are wondering what tools and materials you will need then the answer is that it all depends on what you want to make. To a large extent however, that in turn can be tailored to what you have available. ANYTHING can be useful.
Try not to think in terms of: "I want to make terrain, what do I need?" Have a look at the project articles and you'll see people using all kinds of things. If you see something you want to make then consider gathering together the tools and materials mentioned in the article but also consider making your own version using things that you already have. It is often the case that one terrain modeller will use corrugate cardboard where another will use foamcore and another will use polystyrene, cork, plywood or any one of a number of other things.
There are some tools and materials that crop up over and over again and you can find articles about many of them in our reference section, but check out the projects first. You won't get far through the project articles before you come to realise that for many die-hard terrain builders it's not so much a case of "I want to build X, what do I need?" as being a case of "I've got X, how can I use it to make terrain?"