"Kaleidoscope," evidently, has become a metaphor for many things, mostly displaying changing combinations of patterns, values, and ideas.  But among these, real kaleidoscopes in their original meaning are by far the most interesting and most beautiful.  Invented by Sir David Brewster, a Scotsman, in 1816, the kaleidoscope achieved instant popularity in 19th century Europe.  Hundreds of thousands were sold before the fad died out. 

More than 150 years later, kaleidoscopes are enjoying a renaissance.  Beginning in the late 1970s, and gaining momentum with the publication of the first book on the subject, Through the Kaleidoscope, by Cozy Baker in 1985, kaleidoscopes have taken on an enormous range of forms and styles and become a major new art form. Baker subsequently founded the Brewster Society, and has probably done more than any single individual to popularize the art form. 

The kaleidoscope you probably recall from childhood was a cardboard tube with two mirrors running down its length, containing pieces of colored glass at one end and an eyepiece at the other. If that's what you think of when the term is mentioned, visit a few of the sites linked below to see what contemporary artists have done with the concept. 

The Brewster Society -- an international organization for kaleidoscope enthusiasts.  The best starting point on the web for anyone with a serious interest in kaleidoscopes.  Includes a list of artists, images, history, a nationwide (U.S.) list of retailers, a bibliography, and many other resources.

My own gallery of digital kaleidoscope photographs at PBase.com, similar to the photo at the top of the page, taken through one of the kaleidoscopes in my collection.

Buy Kaleidoscope Artistry, Cozy Baker's latest book, from Amazon.com ($24.47).

Kaleidoscope Heaven -- a site "dedicated toward the understanding and appreciation of kaleidoscopes and those that love them" with information about how to build a kaleidoscope, math and kaleidoscopes, digital photography, and more.  Oddly, there is a banner ad for "the world's best back-scratcher" at the top of the home page to "support the site!"

Kaleidoscope Collector from "Hand of the Craftsman."  A large collection of kaleidoscopes for sale on a pretty site.

Images Kaleidoscopes -- a collection of "themed art" kaleidoscopes.  Examples include holidays, foods and beverages, fauna, and mother nature.  Some beautiful images and animations.

Kaleidoscopes of America by Davlins Gifts of Maple Grove, Minnesota.  The design is less than exciting, but the site contains many resources and links.

Kaleidoscope World, a "cybershop" of The Glass'scope of Red Wing, Minnesota, has a wonderful collection of 'scopes, ranging in price from a dollar to several thousand (also some neat kaleidoscope photographs).

Kaleidoscopes to You, direct from Manly, Iowa.

Two nice kaleidoscope screensavers: the Dreamscope ($12.95) and  the Brewster Kaleidoscopic Screensaver ($16.95).  Many others are available elsewhere on the web.

The Silicon Mirror is a piece of software that operates on digital images like the mirrors inside a kaleidoscope.  The Silicon Kaleidoscope is a screensaver based on the Silicon Mirror. ($12 for both - 30 day evaluation copy available free).  See, also, the Magic Mirror, which does more or less the same thing ($16.95).

Kaleidoworld at Catskill Corners.  The Borscht Belt now features to what is claimed to be the world's largest kaleidoscope -- "a 37.5 foot tall pyramid of mirrors reflecting a constantly evolving Giant Virtual Sphere with a 50 foot wide diameter towering over the heads of viewers."  The site says (believably) that "There is nothing like it in the world!"  General admission $9 per person.

Instructions for making a "Duck Into Kaleidoscope."  Put you head inside it and see "a million faces."  A scary thought, perhaps.  Fun from the Exploratorium in San Francisco.  For an example of the results, see this picture I took of my daughter at a science center in Wisconsin about 10 years ago.