First to a local USB drive (good to take with me on trips).
Second to a NAS in my basement.
Third to a USB drive I left at my in-laws place 3 states away.
It really depends on what you're teaching. If you want to teach them an enterprise product, then RHEL/CentOS/Fedora. If you want to teach them a desktop product, then Ubuntu. I know this probably wouldn't be for the poster, but for others who felt comfortable with Windows and would just want to learn basic Linux commands, dare I commit heresy here, might I suggest Cygwin?