Not an interactive digital resource, but a very useful resource for teaching conics nonetheless. From Lou Talman.

http://clem.mscd.edu/~talmanl/PDFs/Misc/APCalculus/ConicGraphPaper.pdf

Naomi has a triangle which is blue on one side and yellow on the other. It has a dot in one corner on each side.

How many ways are there of posting this triangle through a triangular shaped slot?

http://nrich.maths.org/public/viewer.php?obj_id=2644

Turning Triangles
A triangle ABC resting on a horizontal line is "rolled" along the line. Describe the paths of each of the vertices and the relationships between them and the original triangle. How does the answer change if the triangle is a right-angled triangle or an equilateral triangle?
http://nrich.maths.org/public/viewer.php?obj_id=865&part=

Roundabout
A circle rolls around the outside edge of a square so that its circumference always touches the edge of the square.
Describe the locus of the centre of the circle and its length.
http://nrich.maths.org/public/viewer.php?obj_id=2159&part=

Is There a Theorem?
Draw a square. (This square will be fixed, think of it as being glued to the page.) A second square of the same size slides around the first always maintaining contact and keeping the same orientation. How far does the dot travel?
http://nrich.maths.org/public/viewer.php?obj_id=492&part=

Rollin' Rollin' Rollin;
Two circles of equal radius kiss at the point P. One circle is fixed whilst the other moves, rolling without slipping, all the way round. How many times does the moving coin revolve before returning to P?

What happens if the radius of the moving circle is half that of the fixed circle? Can you generalise your results further?
http://nrich.maths.org/public/viewer.php?obj_id=2162&part=

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

This flash program could be used to introduce simple transformations to the littlies, or an an application of group theory to senior high school students. How cool is that!
http://nrich.maths.org/public/viewer.php?obj_id=5560

Two mind reading activities. The first one can be explained using knowledge of linear expressions, while the second one is just a bit of fun.

A triangle is made up of four pieces. Move the pieces around to make a new congruent triangle. Except the new triangle is missing one square unit! Where did it go?

An interactive animation illustrating the sequence described by the nth term expression, 4n - 1, where n corresponds to the number of potatoes. Drag the potatoes into the microwave to see the time required to cook them. Click the arrow button to reset the animation.
http://www.yenka.com/freecontent/item.action?quick=mb#

A simple but effective tool for plotting points in the first quadrant.
http://www.yenka.com/freecontent/item.action?quick=nc#

Create and solve a linear equation by dragging the green circles up and down. The interactive graphics fill the whole screen so it is great for interactive whiteboards. Solutions must be natural numbers. From Yenka.com
http://www.yenka.com/freecontent/item.action?quick=lv#

These versions show if the equation is balanced or not, but the equation can't be changed.
http://www.yenka.com/freecontent/item.action?quick=lm#
http://www.yenka.com/freecontent/item.action?quick=ls#
http://www.yenka.com/freecontent/item.action?quick=lr#
http://www.yenka.com/freecontent/item.action?quick=ln#
http://www.yenka.com/freecontent/item.action?quick=lu#
http://www.yenka.com/freecontent/item.action?quick=lt#