Well you could install CentOS and search around some basic administrative tasks to learn. If you want to learn anything on Linux, I would recommend at least gaining an understanding of the command ... [by usr_drc]
I have some familiarity with Linux, but I want to start learning it, in more detail, now. I will install something like VirtualBox from Oracle, with Centos, as distro, I think. I've been already testing something like this, end I ended up picking Centos for this.
I have some time that I can invest in this, and I want to do it very good.