As mentioned in previous posts, I'm a big fan of the PhET simulations.
Today, I posted three activities to PhET's teacher-sharing resource. These are PDFs of student pages and notes for classroom activities/virtual labs.
"Worlds of Wonder" can be found at PhET's "My Solar System" simulation description page. First you simulate Newton's Cannon; eventually you find the relationship between orbital radius and orbital speed.
"Quest for the Coulomb Cup" can be found as PhET's "Electric Field Hockey" simulation page. I tried to recreate the student activity I originally wrote to accompany the old, original Ruth Chabay/Academic Software simulation that I can no longer run. This one remains a student favorite.
"Water Waves in an Electric Sink" can be found at PhET's "Wave Interference" simulation page. It allows exploration of the effects of changing the amplitude or frequency of a wave source.