If you use a Mac with multiple monitors and you occasionally disconnect your external monitor, then you know that when you disconnect your external monitor any windows that were on that monitor are sometimes left on that screen and you can't get them.

The blog post in the link below gives a script to fix this problem and instructions on how to use it. If this ever happens again, you run the script and it moves all of your windows on to your main screen. It works very well for me and it solves this very annoying problem.