In this video, Salman Khan of Khan Academy finds the foci of an ellipse.
Khan Academy

Excellent site showing examples of algebra, trig, calculus, differential equations, and linear algebra.
Paul's Online Math Notes

Article on ellipses. Above the level of most students, but useful for the tutor.
MathWorld

A site with step by step tutorials on how to draw and graph a variety of mathematical functions
Analyze Math

Online graphing calculator, useful for drawing out a function to visualize it or find key points.
http://www.coolmath.com

A tutorial which includes a video and several examples for graphing ellipses and writing ellipses equations.
Algebra Lab

In this video, Salman Khan of Khan Academy explains conic sections and ellipses.
Khan Academy

A description of the axes of an ellipse and a formula for finding the length of the axes when given the foci.
Math Open Reference
