AT&T's phone directory has search tools for people, businesses, reverse lookup (by phone, not address), and toll free numbers. Not as up to date as you might hope for, coming from the phone company, but good for established numbers.

This directory server returns an address and phone number for people or businesses. Good backup to AT&T and 555-1212.

It calls itself the ultimate directory. There are search engines for people, reverse address, reverse phone, email and reverse email, area code lookup and reverse area code lookup, businesses, corporate web sites, and government. You'll also find and a range of other interesting items like city guides, apartment finders, point to point maps, and electronic greeting cards.

Find email addresses here.

Another email address server.

Get your Zip + 4 codes right here! Those wonderful public servants at the United States Postal Service have put together a server that dispenses zip codes for specific addresses, postal rates, and other USPS info. If you need to find a company address, enter the company name and the city. The server will return the address with full zip.

CEDAR has an interesting set of utilities related to addresses, including a zip code server and an address correction feature.

Want to know all the zip codes within 100 miles of a particular spot? This is the place to go. Want to know all the zips within a city, county or state? JCS will tell you. They will also tell you all the area code changes in any region.

Similar to Jay Computer Services, but this one gives you the population, cities and zip codes within a user-specified radius of a given zip code.