Scholastic
Scholastic: Study Jams! Science: Force and Motion: Simple Machines
A slideshow and a short quiz on simple machines and how they reduce the amount of work or effort needed to complete a task.
Khan Academy
Khan Academy: Simple Machines and How to Use This Tutorial
There are six simple machines. They are as follows: lever, wheel, pulley, incline plane, wedge, and screw. This tutorial will cover the first three.
University of Houston
University of Houston: Science Lessons: Simple Machines Learning Site
Provides definitions of all 6 simple machines with examples and student drawing of them. Interactive "simple machines quiz" at the end.
Ducksters
Ducksters: Physics for Kids: Simple Machines
Kids learn about the science behind simple machines such as levers, wheels, pulleys, inclined planes, and screws. How they work together to make complex machinery.
Soft Schools
Soft Schools: Simple Machines
Identify the six simple machines by dragging the correct term, and dropping it onto the associated simple machine.
Soft Schools
Soft Schools: Physics Quizzes: Simple Machines
Assess your understanding of the six simple machines with this interactive multiple choice quiz. Immediate feedback is available.
SEDL
Southwest Educational Development Laboratory: Simple Machines [Pdf]
This large PDF file contains seven lessons on simple machines. Includes illustrations. Requires Adobe Reader.