The facilities listed, are in my opinion, most useful for cruisers, which means lots of private resorts are not shown because they don't cater to transient boaters.
Click on the picture and then enlarge it to see dot colors better!
Note on trip planning:
I don't recommend taking your boat on a ferry and launching somewhere in the islands. However if you must, there are county ramps on all four islands served by the ferries except Shaw. Many private resorts have ramps but they are inferior at best, nonfunctional at worst. The one exception is Jackson Beach Park (Port of Friday Harbor) near Friday Harbor on San Juan Island. Jackson has a good double ramp and float and you can park for free up to 72 hours.