Yes, I did a group tour trip to St. Petersburg, Estonia and Latvia (with day ferry trip to Helsinki) last year. We bussed from SP to Tallinn, Estonia and then Riga, Latvia. Both cities are well worth seeing. The bus trip in between the cities is long and the landscape not that interesting, but I found the border crossings to be fascinating. Still very much llke the "Checkpoint Charlies" of the old Soviet days. Kind of scary, actually. At one of the crossings our busdriver got too close too quickly to suit the guards and we were all ordered off the bus with our luggage for a quicky inspection due to his violation. I also noticed a broom leaning next the the building, made out of a bundle of twigs and tied to the stick with twine. Something like you might see here in the states at a quaint country store to use as a wall decoration. Only this makeshift broom was actually used to sweep the road area in front of the checkpoint. It was pretty surreal.

The ferry to Helsinki from Estonia was impressive. It was actually a ship from the Viking line, since we were there in the winter and they were ferrying people across in the big ships that could break the ice. Coming back at night, the scene was straight out of Titanic; huge chunks of ice in the water as far as the eye could see. But the ship was warm and cozy with great restaurants and cocktail lounges.

By all means, go for it, and have a great time!