In the list of guests from Chapter 4 of The Great Gatsby, what further indication is there that old money is in East Egg and new money is in West Egg?

As the answer to your new and exciting question about The Great Gastby, I would have to say that the people from East Egg are described mostly by famous family name while the people from West Egg are described mostly by occupation.  In Nick's list from Chapter 4, the East Eggers are listed as "the Hornbeams" and "the Willie Voltaires" and "the Ismays" and "the Chrysties" and "a whole clan named Blackbuck."  The East Egg list, then, is a list of family names carried through history: all famous because of their wealth.  (Actually, I got a kick out of the mention of the Ismays, wondering if it was referring to the family of Bruce Ismay who bolted from the Titanic in disgrace.)  In regards to West Egg, people are mentioned by first and last name instead of by family.  Also tickling my funny bone is the fact that Nick often specifically mentions the West Eggers who are involved in the performing arts such as:

Arthur McCarty, all connected with the movies in one way or another. (62) 

Nick even describes many others as "theatrical people."  What a subtle difference that makes such a valid point about the differences between the two places!  It is just glorious when a question such as this truly makes an English teacher have to "think."  : )