One idiosyncrasy of Mac OS X is that application windows can only be sized from their lower right corner, and Mac OS does not have any kind of "snap windows into place" feature similar to Windows 7. At work I have the pleasure of working on a large 27" iMac screen, so I frequently arrange two apps side by side while working, or might even have more than 2 apps visible on the screen at any given time. Arranging that kind of setup is tedious when done manually with the mouse, but with a nifty little tool called Divvy the task becomes quite easy. As can be seen in the Divvy in Action video on their site, when activated, Divvy overlays a grid on your screen and can be used to visually size an application to a specific portion of the screen. That is great, but what I found faster and easier was to assign global OS X shortcuts to window arranging operations I frequently use and let Divvy do its magic without bringing up the grid panel at all. Creating shortcuts is covered towards the end of the video, but to make them global you need to check the "Global Shortcut" check box. Here is a screen shot of some of the configurations I set up:
For example if I need to have an application fill the left 50% of my screen I just hit ctrl-shift-1 (with the app in focus) and it will jump right into place. While developing, I often arrange things so that my IDE uses the entire right-side of the screen, the website I am testing covers the upper left-side of the screen and the application sever console (logging output) covers the lower left-side. To put the windows in place I simply put them in focus one at a time and hit ctrl-shift-2, ctrl-shift-3 and ctrl-shift-4, in that order, and the apps snap into place, filling the screen like this:
No space is wasted on the screen and no annoying mouse-dragging operations are needed. Of course you can assign whatever keyboard shortcuts make sense to you.
Divvy is not freeware, but low cost, and can be used in demo mode (periodically pops up a registration message) if you don't want to cough up the $14. It supports multiple monitors and is available for Windows too.