Slicer is an invaluable window management app for OS X.
Watch a demo here: https://www.youtube.com/watch?v=_u7nvEWjZuk
Slicer lets you...
... Slice any window to 2/3, 1/3, 1/2, 1/4, 1/8th screen, etc
... Work beautifully on dual-monitor setups
... Mix and match applications in your layouts
... Use every pixel of your screen for maximum productivity
Most window managers sell for $9-15 dollars, but Slicer is aggressively priced at $2.99 for a limited time! More Info »
This is a great addition to your OS X toolchain along with Alfred, Expandrive, Growl, MenuMeters, etc.
Using three intuitive keyboard shortcuts you can make windows Full Screen or cut them in Halves, Thirds, Quarters, Eights - Slice and dice your windows as much as you want.