Magnetic Schematic lets you create analog circuit diagrams on your
refrigerator, whiteboard, or chalkboard (as long as the surface is magnetic). The set contains representations of basic circuit elements including resistors, capacitors, inductors, diodes, transistors, opamps, wires, and a 555 timer. You can view the full set. Both hobbyists and professionals can use Magnetic Schematic for amusement, design, or teaching.
Magnetic Schematic costs only $19.95 plus shipping.