Curtis Aviation at Camden used to do banner towing (and possibly endorsements too???) in the Citabria many years ago when I was learning to fly (as per Adam's post below, maybe it was the Maule? There's been a few beers between then and now!
). It was spectacular to watch them pick the banner up.
There is nothing on their website to suggest they still do this type of flying. IIRC, it was former owner Steve Curtis who did the flying on the occasions that I saw them do it.