Web sites that I have found that a useful for general eyepiece description and explanation.
This link will lead you to the Bayerbrook Observatory's PDF, by Chris Lord "The Evolution of the Astronomical Eyepiece", a great read and description of the various eyepiece designs and evolution.
This is a useful website allows you to compare various eyepieces and focal length telescopes, and simulates views of the Moon and Saturn.
A very informative primer on the telescope eyepiece with illustrations.
A very good description of most eyepieces with illustrations of eyepiece design, lens arrangement and types of glass used.
A very informative discussion forum, dealing with almost any astronomy topic.
Stellarium is a free open source planetarium for your computer. It shows a realistic sky in 3D, just like what you see with the naked eye, binoculars or a telescope. It is being used in planetarium projectors. Just set your coordinates and go.
Did you ever want to know anything about hand planes? This site documents every model of Stanley non-currrent hand planes.
Oh be still my beating heart...