We recommend our students do something over the summer that they enjoy. Summer breaks offer students the chance to try something new, deepen an interest, or have an experience that may support their academic interests. For example, if they are considering studying education, they might volunteer to work with children. If they enjoy creative writing, they might attend a summer writing program. They may also want to get a job to see what real world experience is like. It's important to do something, and also important to have some down time and family time.
There's not a particular type of summer program that colleges prefer above all; they just want to see that students did some sort of enrichment activity during their time off from school. Finally, students should not try to impress admissions committees with an excessive quantity of summer activities. They prefer meaningful participation in one or two activities, and will be able to see right through any attempts at filling a resume.