Correct Use of Commas
In a series of three or more terms with a single conjunction, use a comma after each term except the last.
-- Strunk and White, The Elements of Style
The dropping of the comma before "and" in a series seems to me a surrender of clarity, giving "red, white and blue" the same rhythm as "tea, bread and butter" or "Chaplin, Laurel and Hardy."
-- John Updike in The New Yorker