Since making the move to Mac, I have discovered and installed some programs that I’ve found quite useful. Here’s one I use every day.
Cinch is a window manager that emulates a feature from Windows 7, which has some nice UI innovations (!). With Cinch installed, you can drag a window to the top of the screen, and it zooms it to fill the screen. The nicest part (which I don’t think Windows does) is that if you drag a window to one side of the screen, it fills exactly that half. Tremendously useful on laptops. Seven bucks, totally worth it.