From what I've gathered from various threads:
6 recipies:
1. Iron Door
2. Wood Pressure PLate
3. Stone Pressure Plate
4. Wall Button
5. Lever
6. Red Torch/Power source
Buttons, red torches, etc, provide power. Placing a button next to an iron door opens it. Red ore placed on the ground turns into wires which conduct power over tiles so you don't need buttons right in front of the door. You can also hook wires up to dynamite which explode when powered. Red torches provide continuos power. Buttons/switches provide power when toggled. You can hold down pressure plates with any entity, even dropped blocks of dirt. You can set up pressure plates in your mines connected to dynamte as traps. Walking over red wires destroyes them as well. You can set up a battery to a set of doors to keep them open, then use wires a tripwire so when people cross them the doors slam closed.