Sketchup from Google is a widely used 3D modelling program. Originally designed to design buildings in Google Earth, it can be used to model anything. There is a vast library of pre-made components to download. So many possible uses in the classroom. Make sure you are using it too!
http://ictmagic.wikispaces.com/ICT+&+Web+Tools
"Free, open source version of Minecraft. Enable 'Creative Mode' to let your pupils to build as their imagination and creativity allows. Download for Windows, Mac or Android devices. The game is supported by a community and a huge set of mods to modify the game for individual needs."