H.I. Sutton's latest article on his Covert Shores website is a survey of submarines with nuclear attack capability in the world today. It's not just the United States and Russia anymore.

From the Covert Shores website:
The dynamics of at-sea nuclear deterrence have completely changed since the end of the Cold War. In those 25 years the total number of active ballistic missile submarines has more than halved. The US Navy used to operate 33 ballistic missile submarines; today it operates just 14. Russian meanwhile has gone from 62 down to just 12, or 13 if you count the last TYPHOON Class which is still used for trials. The United Kingdom and France maintain the absolute minimum at-sea deterrent with just four submarines apiece.