I gave a presentation at Drupal Somerset the other night on some simple tips for using the command line to help with your Drupal development.
I have included the slides here. I have annotated the slides since they don't have the verbal explanations!
Some other refs:
Configure your iTerm to act like Visor - http://technosophos.com/content/configure-iterm2-act-visor
Reference for commands in OSX - http://ss64.com/osx/
View the discussion thread.