Duplicate Windows is an application that allows you to visually duplicate any window in Mac OS X live and on-the-fly. This app is useful for presentations, teaching, live demos, and making web video more convenient on the desktop. Also you can duplicate windows across monitors.
This Mac program helps you resize windows on your desktop.
Windows Live Mesh - keep the folders you choose in sync across your computers.
Clone Window creates a Finder copy of your current window.
This app lets you move and resize your Mac OS X windows with your keyboard.
Resize Safari to a specific window size with a single click.