I have seen other discussions about visas for St. Petersburg but I found an article that says it's no longer necessary, if you stay for less than 72 hours. You just need confirmation from the cruise company that you are with them AND "You are required to depart and return to the port with the tour, you do not have the option to stay in St. Petersburg and return to the ship on your own."
Oh, great... so you still need to sign up for the expensive excursion. I was hoping to avoid that.
Ah, there is one way around that. Apply for a visa to visit as if you were not going on a cruise. At least I think that would work. Apparently, we could get one in about 3 weeks. http://www.st-petersburg-essentialguide.com/russian-visa.html
Does anyone know for sure? And is there really any need for a guide? Especially of the ship is only there for one day? Taxi to the Hermitage?