Tina-TI is the smallest, fastest to learn/easiest to use freeware editor I've seen. It also includes Spice as a big bonus. OrCAD, KiCAD, XCircuit, gSchem, and others allow for much more flexibility, but have a steeper learning curve.
Tina has the same "open and start" easy drag and drop interface as Electronics Workbench (now NI Multisim).