I just used the Two Brothers Race Applet with my Algebra 1B class.
It is a great resource because it really helps the students understand slope as a rate of change.
I linked to it through internet explorer because there is an option in the lower right hand corner of the screen to zoom in and make it bigger to project on the screen.
For a class that is a challenge to get engaged on a good day, it was a worthwhile lesson on the day before a holiday.
It is found under the Resources tab.
Here is the link: