National Council of Teachers of Mathematics
The Math Forum: Ask Dr. Math: Parabola
Dr. Math, in a reply to a student's question, explains how to find the location of the vertex and focus, calculate the distance between the focus and vertex, as well as identify the axis of symmetry and the directix.
Windstream
Ojk's Precalculus Study Page: Parabolas
Good study tutorial about parabolas. There are examples of finding the equation of the parabola or the focal point and directrix that students can examine and attempt.