>>I would strongly recommend not doing it. There are specialized programs out there for parsing addresses, including some that will convert the addresses to USPS standard format.
>>The permuations on how an address can be entered makes the programming for it extreme.
>
>And let's not forget weird street names like the "22 1/2 st" - I've seen such streets in Charlottesville and Virginia Beach.
>
>Doesn't USPS have a webservice where you can submit an address and it comes back normalized, i.e. the way they store it, even adding the four extra digits to the zip? I think I saw it mentioned here once.

Yes, they do. But do check the terms of usage.
http://www.usps.com/webtools/?from=zclsearch&page=webtools
and
http://www.usps.com/webtools/address.htm