Got any tips or tricks for Terminal in Mac OS X? One tip or trick per answer.

My favorite is 

open .


Opens the folder you're currently browsing in Finder. You can also pass URLs, images, documents or else to open.

If you specify a program name with -a you can pass the URL, image, document or folder to that program instead, e.g. open -a Preview image.png, overriding the default program set for the filetype.

Please don't post duplicates. Search in the question like this: inquestion:this ls -l

Mac OS X specific answers only.
You can hold option and click a position in the current line to move your cursor to that position.