This wikipedia page corrects common misquotations -- for example, "Beam me up, Scotty" was never uttered on STAR TREK and Sgt. Friday never said, "Just the facts, ma'am." I am guilty of misquoting the following in the past week or two:
"Power corrupts; absolute power corrupts absolutely."
Notes: This misquote hearkens back to the British Lord Acton, a 19th century English historian who was commenting about tyrant monarchs (Caesar, Henry VIII, Napoleon, various Russian Tsars, etc.). It is probably the single most misquoted statement in the English language. Lord Acton actually wrote: "Power tends to corrupt; absolute power corrupts absolutely. Great men are almost always bad men."
Now the question of whether to be a technically accurate smartypants the next time this quote applies, or to accept common usage and feel a small ping of intellectual remorse. Probably the latter, because of another favorite quote (which is quoted correctly as far as I know): "Be wiser than other people if you can, but do not tell them so." - Lord Chesterfield