Despite a Russian law outlawing the 'promotion' of homosexuality to minors, St Petersburg remains a generally safe place for gay travellers. Hotels are normally problem-free about two men or two women sharing rooms, and while discretion is the safest policy on the streets, there is a thriving gay scene that's worth exploring.
While St Petersburg is liberal by Russian standards, it is still far behind the rest of Europe. It should be no problem at all to book a double room for same-sex couples, although outside top-end hotels you can expect some curiosity from staff. Same-sex public displays of affection are never a good idea, however: always err on the side of caution.
Sadly, homophobia has been steadily growing, stoked by first a local, then a national law prohibiting 'gay propaganda'. While having few legal ramifications for most people, this has unleashed some latent homophobia in a country where so-called 'non-traditional orientations' were previously little discussed and thus largely ignored.
There is a busy and growing gay scene, but it remains fairly discreet. Gay pride marches are routinely attacked by far right groups and the police often harass protesters. Coming Out (www.comingoutspb.com) is the site of a St Petersburg–based support organisation.
A few other useful links:
english.gay.ru The English version of this site includes club listings and tour guides, plus information on gay history and culture in Russia.
www.lesbi.ru An active site for lesbian issues; Russian only.
www.xs.gay.ru The local gay and lesbian portal. Russian only.