Varsity Tutors
Varsity Tutors: Hotmath: Practice Problems: Conic Sections
Hotmath provides 26 practice problems relating to conic sections. Each of the practice problems include a step-by-step guide for solving their conic.
Math Is Fun
Math Is Fun: Conic Sections
Students learn about conic sections. Topics include eccentricity, directrix, and the general equation. The tutorial consists of notes, examples, and practice problems to check for comprehension.
Wolfram Research
Wolfram Math World: Eccentricity
This site explains eccentricity, the quantity defined by a conic section to determine its type of conic section. Has links to related topics.
National Council of Teachers of Mathematics
The Math Forum: Conic Basics
A written description of the different conic sections is described at this site from the Math Forum. The description identifies the importance of the eccentricity in determining the type of conic.