Russian news sources are suggesting that the protests in St Petersburg do after all have a link to the Orange Revolution. Gazeta.ru, newsru.com and others are reporting that protestors have set up some orange children's tents at the intersection of Sadovaya Ulitsa and Nevsky Prospect. Update: Fontanka.ru now says that there are six tents - one large one and five children's ones. They are of various colours - not only orange - and have been moved off the tramlines on to the sidewalk.
There are photographs at Fontanka.ru, but these seem to indicate an increased presence of "NatsBol" (National Bolshevik) supporters, and a general decrease in numbers from yesterday.
There are also reports of demonstrations in Stavropol, where 5,000 protestors blocked the centre of the city, and in Samara.
Veronica Khokhlova has updates here, and here.