Making an app window smaller on a mac
Well, there are some tricks in OS X Lion and above. 

Since OS X Lion you can use any window edge for resizing.

If you hold down the option key, you can also resize a window by expanding or decreasing opposite sides of a window at the same time.

If you hold down the shift key while you expand or contract a window, the window will maintain its original aspect ratio.

Also you can combine option and shift.

If you want keyboard shortcuts (not built-in there) you can use 3rd party software like http://www.macupdate.com/info.php/id/26411/mercurymover.