I just wanted to give a plug for summer music camps. I have been to a few different camps and I always learned a lot and had a great time. In these camps you get one on one instruction from professional teachers and performers, lots of performing opportunities, and you meet lots of people doing the same thing you are...playing music!
http://www2.sewanee.edu/ssmfThe Sewanee Summer Music Festival (SSMF) is a five week music camp in Sewanne, Tennessee for advanced students. There are private lessons, chamber groups, and a full orchestra. The chamber and orchestra groups perform each week and are rearranged so you have the opportunity to learn as much music and work with as many people as possible.
http://suzukiassociation.org/events/loc/65/
The Intermountain Suzuki Strings Institute is a great program. It is located in Salt Lake City, Utah and is a week long program for beginning to advanced students learning the Suzuki method. There are masterclasses with professionals and concerts all week. There are a number of classes available for the students to participate in. Parents are welcome to attend all classes. There is also a week of teacher training for those interested in learning more about teaching the Suzuki method.
I highly encourage kids involved in music to participate in summer music camps. They are a great and fun learning experience!