I can never remember the Laplacians, gradients and divergence formulas in spherical and cylindrical coordinates. Usually I use Griffiths Introduction to Electrodynamics, however I don’t always carry the book with me. As such I am leaving them here as a useful place for me to reference. While there are many places to reference they are usually not front in center.
I hope you find them useful too.
Cylindrical Polar Coordinates
Spherical Polar Coordinates