I went on Peter's walking tours last April having read information about them before leaving. This was the best tour I have ever taken. The guides are incredibly knowledgeable and informative.
The tours take you around St Petersburg using public transport and take groups to unusual sights (we visited an apartment block with art installations and a large bomb shelter) as well as lots of the expected destinations. They even tailor make the tour to suit the group and will happily throw in something extra at a walker's request.
Is this your business?