Ever need to compare two documents side-by-side? In the past, you'd have to manually resize the windows. With Snap, you just drag two windows to either side of your screen and they'll snap into place opposite each other. Snap a window to the top of the screen and it expands to fill the desktop.
With Shake, you can click the top of a window and give your mouse a shake to minimize all the other windows. Shake again, and the other windows return.