A friend of mine (who came from Windows world) have bought a Mac recently and he asked me how to use command line on Mac OS X:
My answer was:
1) 99% of commands are identical in Linux. This is good news as there are a lot of material about it available on the Internet;
2) Terminal.app from OS X is cool, but it’s not perfect. I (and 90% of developers I know) use iTerm2 (http://iterm2.com/). It’s light (3mb), free, open-source, has a better interface than the native one and it rocks! Best terminal I’ve ever used.
3) This is the most useful topic in my answer: an awesome cheat-sheet with command line commands made by the Git-tower team;
4) To finish: I’ve recorded a screencast showing up how to create scripts in OS X and Linux (similar to BAT file in Windows). Unfortunately this is only available in portuguese: