Decoding a Movie’s “Billing Block”

What’s the difference between an executive producer and an associate producer?  Between screenwriters billed as “Smith and Jones” and “Smith & Jones?”  Which actors get an “and” or a “with” or an “as?”  What are all those “in association with” companies on the poster and in the credits?  The New York Times has a very handy guide to a movie’s “billing block,” dictated by an intricate intersection of individual and group contracts and MPAA rulings.