Melissa Data, which enables mass mailers, keeps adding lots of good, free online lookups. Here's its summary of some of the most relevant for journalists:

• Lookup ZIP Codes, city names, the location of phone numbers or the cities covered by an area code.
• Enter a phone number or area code and get city, state, county, time zone and more.
• Search for a street name nationwide. Displays a lists of states and cities with the name with local street address detail.
• Information on over 1,000,000 geographic places.
• State, City and County demographics from the 2000 census.
• Lookup any U.S. address and get the ZIP+4 code, area code, time zone, county, address type, street detail and more.
• Number of home sales and average sell price by ZIP Code.
• Individuals who have contributed to federal campaigns by ZIP Code.
• Monthly low, average and high temperatures by ZIP Code.
• Obtain a list of the ZIP Codes in any county in the United States.
• Display the distance between any two 5-digit ZIP Codes in the United States.
• Display a listing of the ZIP Codes that fall within a radius.
• Display a listing of the Area Code + Prefixes that fall within a radius.
• Income tax information by ZIP Code. Includes average AGI, number of returns, average refund, age & more.
• Information on a nonprofit organizations by ZIP Code. Includes address, revenue, assets, type of foundation and more.
• Current information on Unemployment Rate and Labor Force by ZIP Code.

Here's a CNN article on how lawyers are using jail databases to find clients.

You can get the table of contents of the Federal Register e-mailed to you every day. The Federal Register is a daily compilation of new federal regulations, legal notices and executive orders. Click on "online list mailing archives," then "FEDREGTOC-L." Lots of other General Printing Office publications also have e-mail alerts too.