Mac: One of Mac's most confusing features is the red close button, which you think would shut down an application but often doesn't. RedQuits is a free utility that closes applications when you click the the red close button.
If you're more used to Windows' application-quitting close button functionality, RedQuits will likely be a much welcome utility for you on the Mac that works as described. Now you don't have to resort to going to the system menu bar (or using Cmd+Q) to quit an application fully and free up some memory.
For even more timesaving goodness, when you have mutiple windows of an application open, clicking the red close button will close all of the related windows at once.
(Note: The small application is quickly installed, but I needed to restart my Mac and relaunch RedQuits for the functionality to appear in all applications.)