Mac OS X Lion supports full-screen mode for most apps, something extremely useful.
You can enter and exit the full-screen mode by pressing command-shift-f (at least that works for Google Chrome, check the first comment after the post), or look for the arrows icon on the top right corner of your app window.
Terminal app supports full-screen as well, however the keyboard screenshots do not work as expected. Upon entering the full-screen mode, there isn’t an obvious way to exit it.
You will have to move your mouse/cursor to the top, wait for the menu bar to appear, and click on the arrows icon. Easy, ain’t it, if you just know where to look at!
** Edit: command-option-f also does the trick, thanks johnie.