smallblueprinter is a great online tool that allows students to "design a set of house plan blueprints online with smallblueprinter,
then take a 3D walk through their design,
using an isometric view and print out their plan."
This online tool is quick and easy to use for budding architects/builders of any age.
The other tool available at smallblueprinter is the gardenplanner. You can quickly design a garden plan online with a drag-and-drop interface. There is a small cost for the download version but the online version is presently free. Just use a screen capture tool to save your finished plan.
Great for horticulture programs, design studies, architecture, science, etc....
Other related links:
TMW Interactive Landscape Guide
Visual Landscape Design - Interactive Multimedia Training
Garden Organic for Schools
Green Teacher Magazine
California Foundation for Agriculture in the Classroom