Meaningless Backgrounds
Originally I had this link point to a web page with truly horrible use of background patterns. However, I ended up deciding that it would be unfair to single out one specific author for a design sin committed by many people who were overly eager to jump on a new bandwagon before its implications were understood.
Thus, I have created my own bad page instead. Isn't it fun!
So far, I have found a single site that made appropriate use of background patterns: The Sci-Fi Channel uses various planetary backgrounds to quickly situate the user and communicate "science-fictionness" without hurting the readability of the information itself.