Shiftit
Open Source
ShiftIt is an application for OSX that allows you to quickly manipulate window position and size using keyboard shortcuts.
BetterSnapTool
Commercial
BetterSnapTool allows you to easily manage your window positions and sizes by either dragging them to one of the screen's corners.
Moom
Commercial
Moom allows you to easily move and zoom windows.
Cinch
Commercial
Cinch gives you simple, mouse-driven window management by defining the left, right, and top edges of your screen as 'hot zones'.
HyperDock
Commercial
HyperDock for Mac lets you take a quick look at the windows you have open in each program when you hover over icons in the Dock.
SizeUp
Commercial
SizeUp allows you to quickly resize and position your windows with keyboard shortcuts or a handy menu bar icon.
Compare Divvy with alternatives
Compare BetterSnapTool and Divvy and decide which is most suitable for you.