With SizeUp I found exactly what I need for managing my application windows on Mac OS X.
One of my daily use cases where SizeUp helps me a lot is when I have open many iTerm windows with ssh shells. On my desktop there are often a lot of shells to different machines open and I am working parallel with them.
Irradiated Software also has an tool called Cinchwhich is the mouse driven version of a window management gadget for all who want to have the functionality know from Windows 7. It's using active corners to arrange the windows.
As you can see on the screenshot there are short cuts for all functions. It is possible to split the screen into two or four sections, maximize or center a window.