I need to find all the valid street addresses given particular streets
and towns/zip codes (USA).  I'd like this information to be immediate
and free, just like white pages search engines.  But I can't find one
that allows me to search given just a street name & town.  For
example,  I'd like to know that the valid street addresses for
Mulsberry Street in Wichita KS are #8, 9, 16, 17, 24, and 25 (totally
fictitious example).

Hello,
Unfortunately, I was unable to find a comprehensive, national, free
search for the kind of information you are seeking. It seems like
direct-mail and marketing companies hoard it for their expensive
databases and mailing lists. That said, I was able to find a few
websites that may be useful for you.

http://www.semaphorecorp.com/cgi/form.html
With Semaphore Corp.'s National Address and Zip-Code Finder you can
enter the street, city, and state and get the range of addresses for
that particular street. However, it does not list each address
separately.

http://www.infospace.com/info/reverse.htm?&actnav=org
Infospace's Reverse search allows you to put in a street, city and
state and will list the last know residents of the street. I found
this search to be incomplete. I entered my own street, city and state
and since my address is not listed in any phonebook, I did not appear.
Nonetheless, it does give addresses of people who have their addresses
listed in the local whitepages.

The Dow Jones Home Price Check allows you to search by street, city
and state and get a listing of recent home sales by street address. It
says it goes back to 1988, but I searched a few streets I know and
didn't see transactions past 1996, so it probably depends on location.
http://dowjones.homepricecheck.com/search.jsp?criteria=street

Another option is to search the County Assessors website of the county
of the street/city your interested in. Many Assessors websites allow
property searches by street, resulting in a list of the addresses on
that street. This website list quite a few of county assessors
on-line: http://www.crimcheck.com/freerecords.htm

I hope these sites help you out!

-bluesky

This was an excellent answer - it gave me several possibilities to
choose from, with caveats for each.  I'm all set!  Thanks!

(It IS curious how the white pages searches don't support this... it
is clearly intentional, and I assume to prevent people from using the
information for mailings...)

Another option is offline. Yes the old paper directory route. It is
called "Cole Directory" and is available at almost any library. They
are large bookes and are about the same size as a white pages and is
organized by address or phone number. It is a very popular tool for
marketers. It also rates addresses by property value the bettter
houses are "A". Many a marketer just mails or calls the "A"
properties. Unfortuantely becuase of their size and expense most
libraries will only have their local one. Sometimes state capitols
will have all of the cities at the main branch. You might not be able
to find it local unless you are in that city. I suggest going to your
local library and asking to see one to see if it is worth traveling to
see one for that city. Look up your street to get an idea of how it
works and the info it gives you. -Good Luck

Here is a link to the company that offers these books if this is
research you need to do on an ongoing basis:

http://www.colemarketshare.com/cole_dir.htm

A caveat on the Dow Jones Price check is that it will not even list
the valid addresses for a street in a non-disclosure state.  Kansas,
New Mexico, Texas, Utah and Wyoming are all non-disclosure states.