[greenyoda]

The IRS also has some of these dedicated 5-digit ZIP codes. For example, 00501 is the IRS processing center in Holtsville, NY. (According to Wikipedia, this is also the lowest-number ZIP code currently in use in the US.)

[ProllyInfamous]

Even more interestingly, most IRS ZIP codes are unique from their surrounding cities' (e.g. 70001 within 78xxx surroundings).