• The LED Museum Features a timeline of LED development, and a catalog of LEDs with various emission spectra
• Biased PN Junction Simulation Java applet which shows carrier movement in a biased PN junction

• Sam's Laser FAQ Great resource for all kinds of lasers, including gas and solid state
• Types of Lasers Information on many different types of lasers
• How a Laser Works Information and diagrams explaining ruby lasers and lasing in general
• How Lasers Work An explanation of lasers suited for everyone

laser diodes

• Green Diodes Details on various colors of laser diodes
• Diode Laser Pinouts Information on various diode laser pinouts
• Laser Diode Reference Long document with substantial information on practical laser diode use
• Laser Diode Advice Tips on where to find working laser diodes