The BBC Mission 2110 Roboidz is also a great way to get started.
A great online introduction and interactive is here - more suited for Stage 3 and High School students.
You can print your own 3D Shapes and make them from these nets.Shapes, edges and vertices can be explored at this instructional website.
An excellent activity teaching students how to draw 3D Shapes on dot paper. You can find the lesson here.
You can download many different types of grid and dot paper here.
Match the 3D shapes using pairs.
The buried 3D shapes game is a fun way to end your lesson.