Okay, I hate to argue with the USPS, but no one actually uses all caps. NO one. Maybe computer-generated mailing lists, but no one else. Also, the site Copyright linked to has no commas anywhere in the address. The most common way to address mail is as so:
Jane L. Miller
Miller Associates
1960 W. Chelsea Ave. Ste. 2006
Allentown, PA 18104
Not all address have the "plus four" zip code, but if there is one it's generally separated by a hyphen as so:
Allentown, PA 18104-1271
There is no comma between the state and the postal code.
Also, it is still permissible to spell out the name of the state (Allentown, Pennsylvania 18104). The post office does prefer the two-letter codes, but spelling out the state is better than guessing and using the wrong abbreviation.