What he said...
I can just add an anectdotal from my limited view ... there is a "prospect showcase" coming up next week among some of the better summer leagues. From what I gather, there is a decent scout turnout. You earn that opportunity by being a top performer in a strong summer league - can be particularly valuable if you are from a school that doesn't get a whole lotta love or you didn't perform so well, for whatever reason, in the Spring.