A lot of Windows users who make the switch to Mac, will mis a maximize option of the windows.
A free tool called Better Touch Tool does offer a great solution for this. Install the software and activate the ‘window snapping’ in the advanced settings.
From now on, you just need to drag your window to the top of your screen to maximize it.
A lot of other options are available like snapping to the top / bottom or left / right, just give it a try!
Update: The tool isn’t free anymore, so I started my search for another application, see this blog post.