Is there a beginners guide to Unix from the OS X point of view?
Solution 1:
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".
Solution 2:
This Mac OS X Unix Tutorial has a lot of information in there which you could start from. All in all, I think that if you start up with any of the good resources on Linux (or Unix), you should be able to get up to speed with most aspects of Unix on OS X.
Solution 3:
O'Reilly has several Learning UNIX for Mac OS X books. They were all published several years ago, and the most recent one is for Tiger. But they are still relevant to UNIX, as one of the great things about UNIX is that the fundamentals are quite stable.