Math Medics
S.o.s. Math: Reducing Fractions
Explains step-by-step how to reduce fractions. Gives examples and exercises to practice this skill.
Other
Help With Fractions: Reducing Fractions by Factorization
The rules for reducing fractions using factorization are clearly explained at this website. This is an excellent place to get step by step explanations for working with fractions.
Other
Project Happy Child: Simplifying Fractions Worksheets
At this location there are three simple stories that explain the basic concept of simplifying fractions or finding their lowest terms. Then there are 12 worksheets that increase in difficulty to help students practice this concept.
Wyzant
Wyzant: Fraction Simplifying Calculator
This WyzAnt applet allows the user to input fractions--improper or mixed numbers--and have the calculator reduce the fraction or convert it into a mixed number. A good resource for checking students work.