Blacksmiths produce plate mail armor (sometimes just referred to as plate to avoid confusion with mail armor) for the game's plate-wearing classes: Death Knights, Paladins, and Warriors. To get most of the new patterns, you will have to gain reputation with the Klaxxi in the Dread Wastes, where the quartermaster will give you access to recipes to learn the high-end armor pieces.
Some of the materials you will be using in Blacksmithing are:
Haunting Spirit
Living Steel
Blood Spirit
Spirit of Harmony
Ghost Iron Ore/Bars
Kyparite
Trillium Bar
Generally, the higher the item-level item you produce the more expensive the materials, with only the item-level-496 items requiring the Blood Spirit, and only items with an item level of 476 and higher requiring Living Steel.