Does anyone know what website has an approach guide for any airport?
With SkyVector, simply search for an airport in the US to pull up different plates and airport details.
The IFATC site groups a bunch of helpful information in one place, including SkyVector links. Search for any airport in the world to find airport details, links to approach plates, more plates, and more.
Skyvector is a good resource for US airports as Luca said, but it fails to have any charts for other countries. If you need charts for other airports, I would recommend checking out government AIPs, googling the airport ICAO followed by charts (ex:KMSP Charts), or purchasing a Navigraph subscription for $10 a month which gives you worldwide charts for every airport that has them.
Another good site is https://vau.aero/navdb/chart/WSSS.pdf
Simply replace WSSS with the airport ICAO that you are looking for. It has most airports and it’s easy to use too!