Nice simple Bash programming howto:
Here was where I was going to post the URL, but apparently my post count is too low for the board to allow it. Search for these terms in google, it will take you too a nice howto: "BASH PROGRAMMING HOWTO"
As far as learning UNIX/Linux/BSD in general, is just to use it.
Force yourself to use it instead of Windoze, the learning curve is quite sharp but thankfully short.
Books, FAQ's, and HOWTO's help, but you'll never understand it, without lots of hands on.
Good luck, and enjoy.