Windows 7 has a great windows shifting mechanic for quickly splitting windows around the screen, to be able to use applications side by side.
For OSX I found an Open Source solution here.
It wasn't perfect for my needs, so I forked the source code primarily to add multiple monitor support, and more customized controls which didn't conflict with the applications I used.
Here is the presentation of the current features.
Here is a walkthrough of the source code so you can quickly jump in and add your own customizations.
Feel free to grab the forked source code here.