I’m not sure how long this has been the case, but if you copy an address, say from a web site, and paste it into the first address field (street) in Contacts, Contacts will parse appropriately.

For example, try:

1234 Easy St
Pleasantville, CA 43402

When pasted into Contacts it will correctly place the City, State and Zip into the appropriate fields.

[crarko adds: OK, I’ll admit I don’t know when this was introduced either because I’d long ago stopped looking for it. Nice to know data detectors keeps being improved.]

Source: Mac OSX Hints