Purple Math
Purplemath: Special Factoring: Differences of Squares
Demonstrates how to use the formula for finding the differences of squares, and warns against trying to factor a sum of squares.
Purple Math
Purplemath: Solving Quadratic Equations by Factoring
Demonstrates how to solve quadratics using factoring (that is/the Zero-Product Property). Provides worked examples/and warnings about common mistakes.
Purple Math
Purplemath: Solving Polynomials: How To
Demonstrates the steps involved in solving a general polynomial, including how to use the Rational Roots Test and synthetic division. Points out when using a graphing calculator can be very helpful.
University of Cambridge
University of Cambridge: Nrich: Funny Factorisation
Learning exercise deals with factors and factorization.
Interactive Mathematics
Interactive Mathematics: Common Factor & Difference of Squares
These easy to follow examples demonstrate how to factor algebraic expression using GCF and difference of squares.
Wyzant
Wyzant: Worksheet Index
WyzAnt is a resource of many algebra worksheets. An answer key is available, or you can click on the problem to see the work. Topics include: basic algebra, simplifying, multiplication, exponents, order of operations, negative exponents,...
Wolfram Research
Wolfram Mathworld: Polynomial Factorization
This site discusses factoring of polynomials, giving a general definition, and many links to satisfy unfamiliar terminology. There are however very few examples.