Before the switch to digital cameras, the lens was by far the most important piece of equipment a photographer could own. Today, the importance of lens quality has not dropped at all; a better lens still produces a higher quality image than a mediocre lens. However, with the invention of digital cameras, a greater emphasis is now placed on the body itself than in the days of film.
In any case, the glass you place in front of the camera shapes the image, determines how light will hit your film or sensor, and controls the sharpness of an image. A lens determines what and how your camera sees and it is crucial to have a thorough understanding of the strengths and weaknesses of the lenses you own in order to select the correct one to create the image in your mind.
I own and use the following lenses, listed from wide angle to telephoto. As pages describing each lens are posted, I will link to them from this list.