David Cay Johnston has a fascinating series of articles in the New York Times that uses IRS data to track wealth (adjusted gross income and interest income) by zip code in Connecticut, New Jersey, and New York (Long Island and Westchester):

Wealth in Connecticut

• Article
• Graphic:  Map
• Graphic:  By Zip Code
  • Highest Average AGI:  $378,533 in 06831/Greenwich
  • Lowest Average AGI:  $3,226 in 06123/Hartford

Wealth in New Jersey

• Article
• Graphic:  Map
• Graphic:  By Zip Code
  • Highest Average AGI:  $566,541 in 07976/Morristown (New Vernon)
  • Lowest Average AGI:  $8,750 in 08625/Trenton

Wealth on Long Island, New York

• Article
• Graphic: Map
• Graphic: By Zip Code
  • Highest Average AGI:  $370,670 in 11765/Mill Neck
  • Lowest Average AGI:  $12,464 in 11802/Hicksville

Wealth in Westchester, New York

• Article
• Graphic:  Map
• Graphic:  By Zip Code
  • Highest Average AGI:  $487,737 in 10577/Purchase
  • Lowest Average AGI:  $13,616 in 10545/Maryknoll