SizeUp bills itself as “the missing window manager” for Mac and I totally agree. This nifty utility stays open on your desktop and allows you to quickly throw windows in different places very easily, and maximize them to full screen (without that annoying OSX version of full screen.)
The tool itself costs $12.99 but is well worth it. I use it every day first thing to maximize windows (CTRL+Command+ALT+M). It even has a handy feature that shows you how much time you have saved since you started using it. If you are thinking about the cost benefit, after a few weeks of saving time stretching and maximizing windows, it should pay for itself.
This great utility is by the folks at http://www.irradiatedsoftware.com/ who make a number of great tools/services for OSX.
Packed with tons of options, I think SizeUp is critical for anyone that is trying to use a laptop + monitor combo on a desk, and definitely required for someone that is rocking 2+ monitors at the same time.
Sometimes it is the simple tools that make the biggest difference, but I was amazed to learn that there is no good solution for Mac for this problem.
A full lineup for what is available is below;
If you are still unconvinced, there is basically a freeware option that lets you use the fully working version with a status box that requires you to click continue.