Windows 7 includes a whole slew of new built-in hotkeys. One set I find myself using quite a bit are the Aero Snap keys -- win + up, down, left, and right -- to quickly reposition application windows on my desktop. If you happen to use a Mac and you want the same functionality, Shift It can provide it.
Launch the app, and it sits up in your status bar waiting for hotkeys to be pressed. Shift It offers a few more zones than Aero Snap -- in addition to halves, it also handles splitting your screen in quarters. Windows can also be centered and maximized (labeled "full screen," but it doesn't actual full-screen a la your web browser).
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