Canonâ€™s Digital Learning Center. EF lenses.
Canon has done a great job explaining the EF lens system at the Canon Digital Learning Center. They break down EF lenses into five categories. There is a very useful lens chart PDF to download. L-Series Lenses explained with some great graphics.
In the â€œEF Lens 101â€ Section there is a cool FOV comparison graphic from 15mm to 1200mm. Some really fun graphics to play with in the IS section as well. In all, this is a fun interactive way to learn more about Canon Glass.