Discovery Education
Discovery Education: Web Math: Plots and Geometry
This site provides descriptions and helpful hints regarding conic sections - circles, parabolas, ellipses, and hyperbolas. Content also includes interactive problem solvers complete with a full analysis of the math behind the answer.
National Council of Teachers of Mathematics
The Math Forum: Ask Dr. Math: Graphing Parabolas
Dr. Math helps a student with the plotting and with finding the vertex and line of symmetry of a parabola.