Open Charge Map is so far as I can tell more about the database than the application itself. It is probably the most complete and is also open so we can all edit and update it to improve it over time.
As an alternative Zap Map often comes up as one people like to use for its simplicity.
There are many though, and I never really know where to turn to for the most reliable information with regards charger locations, but also if they're active and running!