The Data Research Group has launched Income Tax List, which allows you to search IRS income and tax data by zip code.  The site also contains various lists, including:

The five richest zip codes with the highest average incomes:

1. New York, NY 10153:  $6,937,350 (31 returns)
2. New York, NY 10152:  $5,026,410 (29 returns)
3. New York, NY 10274:  $4,706,260 (366 returns)
4. New York, NY 10179:  $3,172,930 (27 returns)
5. Miami Beach, FL 33109 $2,483,880  (259 returns)

(For what it's worth, Beverly Hill 90210 ranked 74th, with an average income of $499,050 with 10,497 returns.)

The five poorest zip codes with the lowest average incomes:

1. New York, NY 10105:  -$182,290 (318 returns)
2. Tennessee Colony, TX 75880:  $430 (21 returns)
3. Gatesville, TX 76598:  $870 (23 returns)
4. Allenton, MO 63001:  $1,250 (24 returns)
5. Alden, IL 60001:  $1,450 (11 returns)