Here are two useful resources for mastering the UNIX command line.
s1A.pdf is a from-scratch chapter on using the UNIX command line.
My YouTube Videos shows how to use the UNIX command line and is a good accompaniement to the PDF linked above.
50 Must Used LINUX Commands does a great job of doing a from-scratch presentation of the command line. Bonus: he tells you how to obtain a BASH shell on your Windoze computer box.