We're evaluating the CASS/spatial package right now...and so far we're very impressed.
However, we've run into a bit of a hitch. We have a zillion addresses (number, street name, street prefix, county, and state) but what we don't have is zip codes.
I ran the addresses through the CASS tool, but although CASS matched my addresses with the addresses in CASS, it didn't pull in the zip code. The CASS zip file is empty.
I am 99% sure the tool can add zips to addresses, but I haven't figured it out yet. Any ideas?