National Council of Teachers of Mathematics
The Math Forum: Ask Dr. Math: Parabola Focal Point
Dr. Math discusses some of the "rules" of parabolas that are specific to the focal point.
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.