Good Summer Programs

What are some beneficial summer programs for high schoolers trying to look impressive on their college resume, but don’t want to pay a lot for? I am asking because I have heard of/attended summer programs that cost thousands of dollars, but read that they don’t really benefit you much.

For example, RSI program at MIT. Any program that is very hard to get in and costs little or no money, will be impressive.

Are there any that look good for military/leadership that are competitive to get into? That’s what I’m looking for, because I am planning on applying to the service academies. Thanks! @f2000sa