Is there a beginners guide to Unix from the OS X point of view? I'm hoping to build on my embarrassingly-limited knowledge of the command line, and I know there are a ton of great resources out there. I'm wondering if there are any books or other resources that are tailored specifically to the OS X user running Terminal.

Thanks.
Well, there is always Apple´s official command line guide but back when I learned my way around the Terminal, I found Unix for the beginning Mage (PDF, free) quite entertaining and educational (given it suits your humour). 

If you´d rather go for a book, I´d highly recommend "The Mac OS X Command Line: Unix Under the Hood".