If you’ve had enough of futzing around with your Safari window, check out Maximize from apfelquak. This wonderful Safari 5 extension lets you alter the size of your Safari window with just a click.
This extension allows you to maximize your window, fill the right half of the screen, fill the left half of the screen, arrange all Safari windows intelligently, and shrink Safari to specific dimensions. There is no more need for guess work and dragging around the corner of your browser. All of this is done for you.
You can place a button for each function on your default toolbar, or you can have the extension display a toolbar of its own. It’s your choice, and that’s why I love Maximize.
As of now, this extension is not supported on the Windows version of Safari. Supposedly, this is due to a bug that needs to be fixed in Safari itself.