A collection of four Geogebra files from Greg Bland that will help students understand conics.

Geogebra is a fantastic FREE dynamic geometry program that can be downloaded from
http://geogebra.org

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

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 animation from Lou Talman show how a planar wave-front entering a parabolic reflector is reflected to the focus of the parabola.
http://clem.mscd.edu/~talmanl/HTML/ParabolicReflector.html

This animation from Lou Talman demonstrates the reflection property of the ellipse.
http://clem.mscd.edu/~talmanl/HTML/EllipticReflector.html

This animation from Lou Talman shows how to use the definition of ellipse to trace out such a curve
http://clem.mscd.edu/~talmanl/HTML/Ellipse_Def.html

This lovely animation from Lou Talman shows how a plane intersects a cone to form the curves traditionally known as the "conic sections," - ellipses, parabolae, and hyperbolae.
http://clem.mscd.edu/~talmanl/HTML/ConicSections.html