BetterSnapTool is available in the Mac App Store!!
BetterSnapTool allows you to easily manage your window positions and sizes by either dragging them to one of the screen’s corners or to the top, left or right side of the screen. This enables you to easily maximize your windows, position them side by side or even resize them to quarters of the screen.
Note for OS X 10.9.x users: in case BetterSnapTool doesn’t work for you, please go to System Preferences => Privacy & Security => Privacy => Accessibility and enable BetterSnapTool there (first click the little lock icon on the bottom left)