Lifehacker found a neat site that allows you to Quickly embed an image without hotlinking. Basically to be polite and not link directly to an image on someone else's server when posting it on your blog or in a forum or something, prepend http://imgred.com/ to the start of the full URL. Nifty stuff, wonder how long it'll last though.
This service of course, is not loved by the professional photographers out there.