This may be common knowlege for Unix geeks, but for average Joes this may be lifesaving information.
If a program crashes, you can kill it by right clicking it's dock icon and hitting "Force Quit". If that doesn't work, you can launch "Activity Monitor" and kill a crashing program from there. Just highlight the program that's going down and hit the quit icon, then hit "Force Quit". You can also press Ctrl+Alt+Escape (Command+Option+Escape on a Mac keyboard), choose the application you want to quit and then press the button "Force Quit".
Very good for stopping a runaway Deer Park from taking the system with it as it spirals down...
