Core Bricks are the five bricks that everyone should make first. They are the Battery Brick, LED Brick, Binder Clip Switch, Push Switch, and Dial Switch. Parts for these will come from an LED candle (usually 2 for $1). You will also need some cardboard, 11 small binder clips, 2 paper clips, aluminium foil, glue, and a marker.
Click on the name or picture for directions to make each core brick.
Video of Core Bricks
A supercut of how to take apart an LED and make all five Core Bricks. This is meant to looped (right click and select "loop")