Murphy's Law is usually quoted as "Whatever can go wrong, will go wrong." The law is named in honor of Edward A. Murphy and popularized by John Paul Stapp, but the story is a lot more complicated than that. Nick Spark researched the origins of the law which you can read on the AIR (Annals of Improbable Research) website. There's even a Slashdot discussion on the topic.
Other commonly known sayings referenced in the report:
Peter Principle (by Lawrence Peter): "In a hierarchy every employee tends to rise to his level of incompetence"
Parkinson's Law: "Work expands to meet the time and money that is available"