MovieMistakes.com is one of the rare web sites that has a URL that clearly explains what you’ll find there: Movie Mistakes.  This site contains a compendium of mistakes that can be found in modern cinema.  Editing and consistency mistakes are common in movies and some other sites feature some of the more interesting errors, but this site dedicates it wholly to mistakes and those who find them.  Replete with screen and video capture examples, MovieMistakes.com makes for an interesting visit for film buffs and regular viewers alike.  Of particular note is the Best Mistakes with Pictures section that contains clear examples of some of the best mistakes that made it through to final production.  My favorite is the scene in Pirates of the Carribean: The Curse of the Black Pearl where a crew member donning a cowboy hat is clearly visible looking out over the ocean.

http://www.moviemistakes.com/