Jim Loy
Jl's Math Page: The Golden Rectangle and the Golden Ratio
This is a personal site from Jim Loy that describes the golden rectangle and the golden ratio. Includes several diagrams and pictures as well as formulas. A good background in math is helpful.
Annenberg Foundation
Annenberg Learner: Part C: Fibonacci Numbers
Look at an interesting application of ratios that demonstrates the amazing patterns that emerge when we examine mathematics. The Fibonacci numbers are found in art, music, and nature.