Sherri wrote a thoughtful commentary on teens being bored over the summer. And she is right - about now, teens start getting bored during their summer vacations. The suggestion of talking to your teen and suggesting volunteer work is a good idea. And as parents we need to engage our teen and help him find positive ways to use his time.
I think that we should also let our teen have the experience of being "bored." Boredom can be a positive motivator itself. Teens will realize that they have to take responsibility for their own entertainment and for making choices about how they spend their time. Many times we as parents think we are responsibility to always make sure our teen is either doing something that is good for them or doing something that they have fun doing. But everyone finds a place and time where he feels bored - and learning how to manage that feeling is a good coping skill.
Be available to help your teen come up with ideas about how to deal with summer boredom - but let him do some of the work trying to resolve this himself.