I *think* there might have been one in Stockholm on the cruise I was on, but vaguely remember it not being real convenient for some reason. (Might have simply been that our first stop was the Vasa museum, which didn't work with the shuttle).

Helsinki we didn't have one, but we were also docked right in the harbor at the center of town (advantage of being on a small ship).

Helsinki and Stockholm were fairly easy to use public transportation - except for Stockholm requiring that you have the ticket before you board the bus, then not really providing anywhere to buy one (we ended up hiking down to the next pier down and going in the terminal there where the tourism place there was selling day passes for the bus, in hindsight, for our purposes the stockholm card would have made life easier).