Given isosceles triangle OAP on a coordinate plane, where O is the origin, A lies on the positive x-axis and P is a point in quadrant I. What is the locus of P such that triangle OAP always has an area of 12 square units?
Use the interactive diagram to help you solve this cool problem.
http://nrich.maths.org/public/viewer.php?obj_id=2751&part=index

A fantastic activity by Pam Burke! Students have to draw the graphs of functions on their TI-8x calculator (with an appropriate domain) to create a picture of their own choosing. You can download the worksheet and introductory Powerpoint presentation below.

http://www.geocities.com/pamburke74/PictureThis.pdf
http://www.geocities.com/pamburke74/PictureThis.ppt

Who is putting their hand up to transfer this activity to the TI-Nspire calculator? :-)

In this cooperative learning activity, students are presented with a real-world problem: Given a mirror and laser pointer, determine the position where one should stand so that a reflected light image will hit a designated target.

This investigation allows students to develop several rational functions that models three specific forms of a rational function. Students explore the relationship between the graph, the equation, and problem context. From NCTM Illuminations.
http://illuminations.nctm.org/LessonDetail.aspx?ID=L606

Explore the graphs of functions interactively.
http://nlvm.usu.edu/en/nav/frames_asid_109_g_3_t_1.html?open=activities&...

Choose the Displacement-Time Graph Game. Move the car to draw the displacement-time graph. Once you understand the connection between the movement of the car and its related graph, test yourself by playing one of the games.
http://www.echalk.co.uk/