posted 23 years ago
Hi,
Which version of UNIX do you want to learn? The best way is to install it on your machine(preferably with someone who knows how to!) and start playing about with it.
Depending on what you want to learn about UNIX(programming, shell scripting, administration, networking) you can start with the basics of the same.
About free downloads, it depends on which UNIX clone you want to learn but there is plenty of documentation on Linux as well as all the BSDs on their respective web sites.
Good luck!
Amol