Sometimes, the operating system Linux comes up in classes. The problem many students have is that they don't necessarily have an extra machine hanging around to install Linux on, so therefore, they never get the chance to experiment with it.
However, there is another way. One distribution (version) of Linux is called Knoppix, and it is specifically designed to fit on a CD. You burn it on to a CD and then boot off of it, and that's it. No installation of anything on your hard drive, and like most versions of Linux, it's free. It's a great way to test drive an operating system that we really don't do anything with in our IT program.
It can be downloaded below. Note that the ISO image is about 700 MB, so it may take a while to download.