Teslarati is pretty useful for locating destination chargers as well as seeing what the amenities are around the superchargers. A couple of times I've referred to it trying to find a hidden supercharger that the navigation system didn't have located correctly. Plugshare also seems to be a popular one for those that don't have good access to superchargers.
Beware of some of them that "poll" the vehicle on a frequent basis as the vampiric drain from the constant inquiries can use up 20-30 miles a day of range. (No personal experience with this, just based on what I've read in other posts)