Some Useful Unix Links to help you get started:

General Unix Links:
Unix tutorial for beginners

Unix for beginners by Gerard J. Kleywegt (written by an X-ray crystallographer). Comprehensive.

Unix for beginners by Ian Tickle (written by an X-ray crystallographer). Some Dos/unix conversions.

Unixhelp for Users  Edinburgh Univ.  (a bit more advanced)

A note about Unix Shells  My page.  (brief notes about [t]csh vs. sh-type shells).

Apple's Command Line Primer covers basic shell concepts, frequently used commands, environment variables, and running programs.

General Unix Books:

Learning the Unix Operating System, 5th ed.  (good for the absolute beginner).

Using csh and tcsh (the next most basic book, but has a lot of useful stuff in it). tcsh was the default shell in Jaguar and is available in Panther.  (Use chsh -s /bin/tcsh to switch back to it.)

Guide to zsh (A free, on-line, and extremely well-written pdf and html book on the best shell ever invented.)

From Bash to Z shell An excellent more advanced introductory book, written by the zsh folks, that gives a highly useful introduction to bash (the default shell in Panther and Tiger) and zsh (what should have been the default shell in Panther and Tiger).

Unix in a Nutshell (a useful reference).

Augmenting Unix on OS X

Here are a set of pages with copious links that I put together that describe how to install Apple's X-windows, gcc and g77 compilers, the package manager system called Fink, and a few other things. Although these enhancements are not "required" to use unix on OS X, you will soon find that you cannot live without them.

Books and tutorials specific to Mac OS X Unix:

Mac OS X has brought the world of unix to a new set of users, and it has some non-canonical quirks.  Here are some helpful books:

Learning Unix for Mac OS X, 2nd Edition  (Very basic treatment for an absolute beginner.)

O'Reilly Mac Dev Center: Unix on Mac OS X, 2nd Edition  (A nice collection of resources, from beginning to advanced.)

Mac OS X for Unix Geeks  (introduce OS X to unix-oriented folks).

Unix for Mac OS X:  Visual QuickPro Guide -- a couple of chapers are on line here:  Unix for Mac OS X

OS X Unleashed, 4th ed. (basic to advanced). A large, very comprehensive book with stuff for beginners and more seasoned folks.

Gary Kerbaugh's Picks: A Valuable Suggested Reading List for OS X Unix

Bash on Mac OS X: O'Reilly tutorial

Zsh on OS X (My propaganda and how-to page for using the best user shell ever invented on the best operating system ever invented).

Some customization suggestions:

Here are some OS X applications and hacks that I can't live without.

Here are some ways to make the terminal-finder interactions more integrated.

Configuring zsh on OS X is easy with these drop-in scripts that work "out of the box."

Shell Scripting and scripting languages:

Unix shell commands can be put together to make fairly elaborate programs that you execute from a file called a shell script.  These programs do not need to be compiled and are generally pretty easy to read and modify for your own needs. Here are a few places to start:

Apple's shell scripting primer

Unix shell scripting

Mendel Cooper's Advanced Bash Scripting Guide (A definitive source for sh-type scripting.)

Python scripting tutorial