I’m considering taking Artificial Intelligence.(https://summerinstitutes.stanford.edu/courses/high-school/Computer-Science#department-934) How is it? Anyone who took it?
I personally had an amazing experience. I took Computer Simulations and Interactive Media, so I’m unable to comment specifically on that course, but I’m sure A.I.'s just as great. I made friends from all over the world, learned college-level concepts, and got to live at Stanford! What more can one ask for?
I went there the summer after sophomore year and studied cryptography (mathematics). It was one of the best experiences of my life and I highly recommend it if you have the resources to. However, I will say that participating in this does not guarantee admission into Stanford, nor do you gain college credit. It shows that you take the initiative and like to go beyond your school curriculum, that’s it.
Nevertheless, it was fun 
My ds attended the summer after his sophomore year and loved it. Took a different class, though. Made great friends, some of whom are with him in his class at Stanford. He did do a for-credit program (6 hours of college credit) at another university the following summer. I think summer academic programs on college campuses are beneficial in gaining a sense of independence and dorm life.
Have you looked at SHI? DD did it, and it’s the one that you actually have to apply, and be accepted, to attend. I think there was a writing sample, teacher recs, etc. if you’re just looking for a great summer program, then I’m sure you’ll have a fantastic time, but if you’re also hoping that it just might help a teensy bit with your app, then look at SHI. I have heard from DD that way more than 5% of the kids got in - informally, possibly 30-40%. Disclaimer, this is one person’s perspective, but I believe that this is the humanities version of Stanford’s high intensity math camp (which also has above average admit rates).
SHI? @Thetwins
Yes, that one.