PBS has a great site on Physics of the Circus. The site is a companion to their show Circus, which you can watch on the site.
The site has resources, lesson plans, video clips, and more on Physics related to the circus. They are organized by concept area, such as Projectile Motion, Newton's Laws, Conservation of Energy and more.
Since most students have seen a circus on TV or been to one, this is a good way to make physics engaging and relate it to something they know.
