Would you know what to do if someone suddenly collapsed in front of you? This web site combines very realistic videos with choice points that allow you to see what happens if you do various wrong (and right) things when a man suddenly has a heart attack in front of you. (One of your options is even "freak out"!)
It doesn't take long, and it's very confidence-building. It might help you to save someone's life. Or at least prevent you from freaking out!