References

Agilent Technologies' Interactive Application Notes provide interesting demonstrations and valuable insights.
Courtesy of Agilent Technologies

S-parameter matching networks : a good description of S-parameters and their use in amplifier and oscillator designs.

Impedance Matching Game : You must try this! It's a Java applet impedance matching model, where Smith Charts are used to visualize the interactive process of impedance matching.

Spectrum Analysis: Amplitude & Frequency Modulation

AM Modulation : Java applet

FM Modulation : Java applet

ECE Electronics Service Shop's Part Store has Parts List and other useful links.
GNU Radio