Here is shown a Do It Yourself kit for making silicon atoms and crystals to demonstrate how semiconductor crystals work and how they are used to make transistor switches.
http://www.virlab.virginia.edu/VL/MOS_kit.htm
Depicts the step-by-step process by which the transistors of an integrated circuit are made.
http://www.virlab.virginia.edu/VL/Semiconductor_science/IC_process/IC_process.htm
An LED is the device shown above. Besides red, they can also be yellow, green and blue. The letters LED stand for Light Emitting Diode.
http://www.iguanalabs.com/1stled.htm
full guide by Cyber Circuits.
http://www.uslink.net/~cybercir/cir23.htm
insight into Ohm's law, Kirchoff's law, LED calculations and voltage dividers
http://www.wd5gnr.com/basiccir.htm
http://www.rlocman.com.ru/am/a02009.htm
A large reference of schematic symbols and brief explanations of each.
http://www.aaroncake.net/electronics/schem.htm
http://hem.passagen.se/sm0vpo/begin/calc-00.htm