[youtube=http://www.youtube.com/watch?v=qPt0X5s-1JU]

Makezine_COTM_October-PowerSupplyMan, no one lays it out like Collin Cunningham! This classic video has Collin describing power supplies and walking through building a dual linear regulated power supply from a kit, describing the individual components, and making some safety suggestions about dealing with mains voltage. Finally, he explains switching power supplies.