Teenagers describe their perceptions of computing as boring, anti-social, and irrelevant to their lives. We are working on a broadening participation in computing project to portray computing as an innovative, creative, and challenging field with authentic, real-world applications. We have developed an Introduction to HCI course for teenagers in which they will participate in design-based projects using end user development tools on the web. The increasing availability of web-based software for creating mashups offers an opportunity to engage teenagers in computing by meeting them in their existing informal and fun environments on the web.