3D design is going to be a very important skill set for the future. Many school districts across the country are already investing in 3D printers as part of their STEM curriculum. The concept is pretty simple. Design something in the virtual world then print it out in the physical one. There are quite a few options when it comes to 3D design software, but none of them are as easy to work with a UseCubes.
UseCubes.com is a free website (or Chrome Extension) that lets users design 3D objects with the drag of a mouse. Click anywhere on the screen to start, then drag your mouse in the direction you want to build. The site will fill in cubes in real time allowing you to create block based designs with ease. It truly is cube based though, as the name implies. There are no other shapes to work with. The design style is similar to what students see in Minecraft so you may find they pick it up quicker than other 3D tools. The one downside I saw was that you could not print out your creation on your own 3D printer. You can send it to print through the a third party though.
Take a moment to check out UseCubes.com and unleash your block based creativity.