If you have a tendency to accidentally X out of your entire browser with all its tabs by an errant flick of the mouse, then this site as one of your tabs (need to click one for Chrome, as it notes) will have a popup asking if you're sure you want to close everything, letting you prevent that.
Do you know of any obscure useful websites?
SEO has essentially destroyed search engines, what are some very useful websites that you might not get given by Google?