Ratio Stadium
Ratio Stadium is an additive arcade game in which the players have to find ratios that are equivalent to each other - and do it fast and accurately. Play against friends, against the computer or against other ratio addicts around the world. Addictive and great fun - three thumbs up!
http://arcademicskillbuilders.com/games/ratio-stadium/ratio-stadium.html

Ratio Blaster
Ratio Blaster is a one-person Space Invaders type game. How quickly can you blast the equivalent fractions out of the sky? Three thumbs up!
http://www.arcademicskillbuilders.com/games/ratio-blaster/ratio-blaster....

First choose the front and rear wheels of the bike, and then start pedalling. How far do you go?

http://illuminations.nctm.org/ActivityDetail.aspx?ID=178

Join together cogs of different sizes and investigate what happens when you turn them. From the NRich website.
http://nrich.maths.org/public/viewer.php?obj_id=4771&part=note

This is a series of interactive pages on distance-time graphs. It is like having a motion sensor when you don't have a motion sensor.

Take Your Dog for a Walk
A clever interactive introduction to rate via distance-time graphs. The full-screen version would be useful if this is done as a whole class activity.
http://nrich.maths.org/public/viewer.php?obj_id=4803

Motion Capture
Motion capture is a similar program but graphs displacement rather than distance, so it may be useful to introduce the concept of first and second derivatives.
http://nrich.maths.org/public/viewer.php?obj_id=4873&part=

Motion Sensor
Motion Sensor tests for understanding - can you describe how a graph was made?
http://nrich.maths.org/public/viewer.php?obj_id=4872&part=

Steady Free Fall
In this rich activity, you drop a ball onto a ramp of your own design and see the graph of vertical distance versus time. Some challenging questions are asked.
http://nrich.maths.org/public/viewer.php?obj_id=4851&part=