Minecraft wiki entry for Redstone_mechanics, associated text: Redstone Dust is the core of redstone mechanics. Mined from redstone ore, the dust can be placed to form "redstone wires" to carry signals, or crafted into other devices.
Components lists and describes the various blocks which interacts with or are affected by redstone power.
Redstone Circuits covers the basics of redstone circuitry, including summaries of the basic circuit types and the blocks (e.g., doors, pistons) which can be controlled by redstone.
Tutorials/Mechanisms lists and describes a variety of more complex projects that can be made with redstone.