Here's a page on a 'Data Quality' service provider that's worth a look:
http://www.melissadata.com/Lookups/addressverify.asp
If you enter an address, you will get the following - the ones with my * in front - I think are useful in the users screen to profile your user base:
Address
*Area Code
Carrier Route - DPC
*Address Type
ZIP Code Type
*County (FIPS Code)
*Time Zone (Local time)
*Consolidated Metro Area (CMSA)
*Primary Metro Area (PMSA)
Representative, Party & District
# (useful for a political site maybe)
Delivery Post Office
Latitude
Longitude
Census Tract
CMSA is VERY broad - I live half way up Connecticut and am in the Bridgeport PMSA and the NEW YORK CMSA.
Address and carrier route are for snail mail support - and there is more stuff you can buy.
My point being - I have this table of data in OACS - stuff users type in and provide. At some point the guy in marketing says - how many of our users are on the east coast? I say - well if you let me send our data out for geocoding I can let you know. From that point on you send incremental files once a month or whatever, but you always can determine how many users are in what regions. Time Zone as I said, is useful if you decide to call the person.
Latitude and Longitude are good if you are going to use any mapping applications.
The point being - I am hoping to have the "address" information *as it is currently viewed by data companies* stored in an isolated area - that way its a lot easier to do what companies actually do - send it out to get checked and coded, without worrying about the relation integrity issues of all the other tables it touches.
I think that what Jon and Matthew are proposing will support that - I just want to make you aware that this additional information should NOT just be discounted as "marketing" stuff - it is part of the physical reality of the address in question, and it makes it easier for marketing to accurately identify the user population of their site - where do they live? What city? What time zone? How many are within 50/500/5000 miles of me or any of my locations?
Nobody that I know of provides this info en masse for free, GPL or whatever, but even the non-profits I work with have enough budget to save themselves money on mailings to pay for the geocoding and address verification.
It's current best practice, it pays for itself, and I think its a mistake to leave it out of the primary location we intend to store addresses :)
