You need your high school coach to start writing letters and making phone calls to colleges that you are interested in, and/or colleges that he has connections with. In addition, talk to your summer coach about other coaches and scouts that he might know. It's all about networking: talk to as many people involved in baseball as you can, and make your intentions known to them. If possible, go to open tryouts and talk to the scouts there about your aspirations. Very often pro scouts will have plenty of connections with college coaches, and are aware of who needs what and where you might fit best. If there are no tryouts in your area, see about going to a camp or clinic; very often there are coaches and scouts there too.
Be courteous and make friends with all scouts and coaches along the way ... you never know who might be able to help you. (And it's always good to have a lot of friends.)