screen

I've been using screen for about two weeks and it's working out quite nicely for me. Before I would have between four and six terminal windows open, constantly Command+~ between them. The effort expended to learn its commands was not extreme, and worth it. The switch to screen instead of multiple terminal windows was partially fueled by the inherent 'leet-ness of it, and also due to several recently blogged about tutorials:

http://www.kuro5hin.org/story/2004/3/9/16838/14935

http://www.redhatmagazine.com/2007/09/27/a-guide-to-gnu-screen/

So if you're the type of person who likes to rock out on the command line I recommend you give it a go. What have you got to lose?