AquaSnap - Too many windows on your screen? Stop wasting your productivity.
i3 - A dynamic tiling window manager designed for X11, inspired by wmii, and written in C.
Mizage Divvy - Divvy is an entirely new way of managing your workspace.
Xmonad - xmonad is a dynamically tiling X11 window manager that is written and configured in Haskell.
Moom - Move your mouse over the green zoom button in any window, and Moom's mouse control overlay will appear (as seen in the above animation).
awesome - A dynamic window manager for the X Window System developed in the C and Lua programming languages.