This is a very simple Java applet in which students fill a box with cubes, layer upon layer, to visualize how volume is calculated in a rectangular prism.

This is a simpler version of volume in rectangular prisms. Students manipulate two solid rectangles (shown side-by-side) to see the effect that even a small change in length/width will have on volume. Values are computed automatically in this applet.

This standards-based lesson for grades 6-8 lets students calculate and compare volumes of cylinders and rectangular prisms using bales of hay as the common unit.