Craig Hockenberry has a lengthy post up about his favorite things in the Terminal. It's so full of greatness it's hard to pick one tip to highlight. I love this kind of thing because it's helpful and it's written in a unique voice.
The command line also responds to control keys. The ones I use the most are Control-A and Control-E to move to the beginning and end of the line. Control-U and Control-K are also useful to delete text from the cursor to the beginning and end of the line buffer. I've heard that these are standard emacs key bindings, but can't confirm this since I'm a vi LOVER NOT A LOSER