I've started with some basic concepts. Although the ideas involved are abstract, they make sense with good demonstrations. I've suggested some lesson plans, as well as short videos.
The Moon looks like a bright object that changes shape, but it's a rocky body that can't emit light, just reflect sunlight.
The Moon is spherical and it orbits the Earth. Therefore the angle of our view of the sunlit half of the Moon changes as it moves.
The same side of the Moon always faces us because it turns on its axis once as it goes around the Earth.
Eclipses don't happen every month because usually the Sun, Earth and Moon aren't quite lined up. The Moon’s orbit is slightly tilted with respect to Earth’s orbit. The orbits cross at two points called nodes. If a full moon or a new moon occurs at these nodes, only then are the three bodies lined up for an eclipse.
The Moon orbits the Earth in 27 days, but it takes 29.5 days to get from new moon to new moon. Since the Earth is also moving in its orbit, the Moon has to travel farther to complete its cycle of phases.
Click on the link to access the material.
(1) Educator's Guide to Moon Phases. The Jet Propulsion Laboratory has prepared this simple, but useful, activity. It recognizes some of the pitfalls in teaching the topic, though you may find that getting the classroom dark enough is your biggest headache. (If so, it's worth negotiating with colleagues to try to get somewhere suitable.)
(2) The Lunar and Planetary Institute. There are a number of activities here. For each one you are told for which age range it is suitable, the time and materials required, and how to run the lesson.
There is a basic lesson in which the children are asked to observe and record moon phases by actually looking at the sky. Hurrah! "Fruit for Phases" is the same idea as the JPL activity and could be done with or without "The Girl Who Married the Moon." Using the story could work nicely in a primary classroom if you are planning crosscurricular work.
If you want to include eclipses, consider "Fruit Loops: Exploring our Moon's Phases and the Reason for Eclipses." Do use the hoops or rings. They're essential to show that the orbit of the Earth and the Moon are tilted with respect to each other, which is why we don't have eclipses every month.
For Grades 8 and above, consider "Golf Ball Phases and Embroidery Hoop Eclipses" or activity (3).
(3) Modeling Eclipses.
Designed by Dennis Schatz of the Pacific Science Center, this also uses hoops for orbits.
(1) Why Does the Moon Look Like It Changes? Ask an Astronomer and she'll tell you why the same side of the Moon always faces us. Only four of the moon phases are named and labelled.
(2) What is an eclipse? This is good, but brief. It shows the planes of the orbits of the Earth and the Moon, but doesn't point out the 'nodes' where the two orbits intersect. These are where eclipses may occur.
(3) What Causes an Eclipse of the Moon? The astronomer explains how lunar eclipses are caused by Earth's shadow.
(4) Why Are Solar Eclipses Only Visible in Some Places?
(1) Lunar Phases, or in Spanish, Fases de la Luna. This takes the learner through three activities to understand the phases of the Moon. It's very good.
(2) Earth and Moon Viewer. This page shows the current moon phase. If you want to change the date, time or place, scroll down the page.
(3) Here's an extension activity to (2). Apollo 11 astronaut Michael Collins used to have a little picture of a crescent-shaped body on his wall. Even though the coloring was wrong, people identified it as the Moon. It was the Earth. See the current phase of the Earth as viewed from the Moon. How are the phases of the two bodies related?
(3) Enchanted Learning. Printable worksheets with diagrams to label of solar eclipses and lunar eclipses Suitable for Grades 7-8.
(4) NASA Starchild. An online quiz to identify and order Moon phases.