I’ve started to make a list of the most common resources I use for PG. Hopefully you can find these useful as well.
Slack channel — Slack is a great resource to get a question or idea answered. Literally thousands of PG professionals using it and available for questions and answers.
Discord Server — Great place to chat and network with others in the community. If you use Discord frequently this is a good place to get answers.
PG Docs — The well known and very informative Docs. These should be referred too often.
Gui for Explain plans — Probably one of the most useful websites to give you a visual representation of your Explain plan. VERY helpful!
Postgres Weekly — Great newsletter that will help you to get a lot of good blog/writing content in your email each week.