I've often used WriteRoom for distraction-free text editing, but I've often wanted the same full-screen experience with Terminal.app. While Terminal.app does not support this behavior, one can create a reasonable approximation using X11.app and xterm. Here is how to set it up:
Open up the X11.app plist using the Property List Editor.app:
> open -a /Developer/Applications/Utilities/Property\ List\ Editor.app ~/Library/Preferences/org.x.X11.plistMake the following edits:
Next, set up a .xinitrc file to launch an xterm instance at the launch of X11.app, specifying the default size of the window. (Note the settings listed here are specific to my 15'' MacBook Pro with the default font and font-size.):
> echo 'exec xterm -geometry 239x69' > ~/.xinitrcRestart X11.app and you should find yourself with a fullscreen terminal session. (Remember, to toggle out of full screen mode, use Command-Option-A)
Additional .xinitrc configurations: