For Superchargers, your Tesla does that for you during navigation, and it even displays nearby Superchargers along with the number of open stalls. For maximum efficiency, it’s best to navigate to a Supercharger (either directly or as an automatically selected waypoint) as that also lets the Tesla pre-condition the battery for faster charging. While the car is pre-conditioning, you may hear a different whining sound, at least on a Model 3 AWD, as this is done by making the front motor a little less efficient to generate more heat to warm the battery. This does in fact use more battery, but if you’re going to a Supercharger, that’s not a big issue. There are also several third party websites that provide this map, including “Superchargers for Tesla” (iOS app, Android app) by Ndili Technologies.
For others, there following services are quite handy: