After researching for this myself, I have found that The Postal Bulletin somewhat states that there will be information printed on the back.
http://about.usps.com/postal-bulletin/pb2013.htmIt is in the stamp issuance section. Currently it's the "stamp services" section.
On the grid for the new stamp announcements, Then it's the last field under "Back". The muscle cars stamp is a little more detailed than usual, normally it says only "Verso Text".
As for anything else, I haven't seen such. It looks like only commemorative stamps for 1st class has this that I know of thus far.
Also, in my very limited experience, I've seen the text behind every stamp on Scouting, but that issue doesn't mention anything about it being in that format.
Unless someone corrects me, the key word is "Verso Text" on that back field, when that's not in the field, there's no paragraphs of text.