Over the years, Instructables has grown and evolved to a site that is both an invaluable resource and a powerful tool for teachers of many practical subjects.
This Instructable is mainly aimed at teachers of all kinds, but students can read it as well, then pass on ideas to their teachers...
All pictures are sourced from either the site itself, or Wikipedia Commons, or created by me, unless otherwise stated.
Step 1: Sign up!
If you use your school email account to drop a line to teachers[at]instructables[dot]com, and let them know that you are actually a teacher, you will be rewarded with a free Pro account.
That will give you access to PDF files (potentially very useful in class) and all-steps display of projects (also useful if showing projects on-screen in class).