Slate is a free, open source window manager for Mac OS X. In short, it binds key combinations to make it a bit easier to manage your application's windows.
An example is: ALT Left Arrow will move the current focused window left 10% (by default). This is the default configuration file and you'll more than likely want to begin editing it right away. You can simply place this file in ~/.slate and begin editing it with your preferences. The very first thing I had to change was CMD Arrow because I, like everyone else on planet earth, use that to move my cursor to the beginning or end of a line. Slate hijacks that and has you switching windows. I do not know why that is in there by default as it is a bit jarring but the application's author must prefer that.
I don't know if Slate will stick with me but I tried it because he said so.