Forces in Action: Try this activity exploring mass, friction, and motion: link.
Friction: Try this friction activity: link
Racing Ball Activity - which ball will win the race?
Reaction Time - How fast can you react? How fast can you stop?
Momentum - adjust the mass and speed of the two vehicles and watch what happens.
Leaning Tower of Pisa - drop things off the tower, just like Gallileo
Collisions - change the mass and velocity of two balls and watch what happens
Crash Test Dummies - always entertaining!
Websites with a variety of activities - look for activities that relate to the topics covered in class (force, motion, work, inertia, speed, velocity, acceleration, etc.).
Fear of Physics - lots of good activities here
Physics Lessons - more things to try - go to "i-physics" and then "1-19 Mechanics" on the drop-down menu
Amusement Park Physics - design your own amusement park rides
PhysLab.net - more activities to try
More... more to try