Local anchorages are local rules. I see one local cruising guide posted above, I'm sure there are others as well in such popular sailing grounds.
Also, try the Interactive Cruising Guide on this website:
Not only will it show anchorages, but you can read other opinions about the quality of holding, etc. It is a bit like the travel review sites, so you have to sort through it a bit and not take every post like absolute fact.
Occasionally, there are free docks for a very limited time, if a township is trying to get you to come shopping or a restaurant has its own dock for customers. These are very few and even further between.