Problem of the Minimum Rotation Surface
Java applet demonstrating the catenary.

Geometry in Action
Includes collections from various areas in which ideas from discrete and computational geometry meet real world applications.

The Geometry Junkyard
Usenet clippings, web pointers, lecture notes, research excerpts, papers, abstracts, programs, problems, and other stuff related to discrete and computational geometry.

Erich's Packing Center
Graphics and links for various packing, tiling and covering problems.

Tim Lister's Hyperbolic Geometry
Cabri constructions for the demonstration of the basic concepts of hyperbolic geometry in the Poincare disc model.

Bette Veteto's Homepage
History of Mathematics, very strong on geometry.

Steiner Surfaces
Mathematical descriptions and ray-traced images of various types of Steiner surfaces

Mathematical Surfaces
A collection of parametric and implicit equations.

Bob's Pages
A collection of interactive geometry applets. Topics include polyhedra, Poncelet's porism, Soddy's hexlet, Mandelbrot set, Steiner porism, Pappus's chain, Repulsion polyhedra and stereo pictures.

Wilson Stothers' Inversive Geometry and CabriJava Pages
Includes Steiner's Porism and the arbelos.

Allexperts Geometry Q&A
Volunteer tutors help you work through your geometry problems for free.

Intensified Geometry Curriculum Review
A comprehensive, illustrated review of concepts covered in an Intensified Geometry textbook/class.

Diamond Theory
Plato tells how Socrates helped Meno's slave boy "remember" the geometry of a diamond. Twenty-four centuries later, this geometry has a new theorem.

Packomania
Includes packings of equal objects in containers together with source codes to obtain them numerically.

Math 3210 - Higher Geometry I
Course notes by Bill Cherowitzo.

Cuboid and Cube Surface Distances
A java applet with substantial analysis related to distances on a rectangular box.

Geometry Page from Interactive Mathematics Miscellany
Includes articles on topics in elementary and not so elementary geometry, many with interactive Java illustrations and multiple proofs.

Morley's Miracle
A discussion of Morley's famous theorem and the research of which it was a tiny part. 5 proofs are given including J. Conway's, D. Newman's, and A. Connes'.

Math Forum: Search geometry-forum
Those interested in examining the previous incarnation of the Math Forum may search the archives of the Geometry Forum.

Geometry Activities
By Ephraim Fithian.

Center of Points in 2- or Higher-dimensional Space
It provides important formulations for finding a center of points in 2 or higher dimensional space. It can be used in drawing delauney triagulation and voronoi diagram in two or higher dimensions. It also describes how many points are required in defining a center in n-dimensional space.

Paul Bourke's Geometry Page
Includes formulas, definitions and three dimensional image illustrations.

Xah's Personal Page
Features an illustrated dictionary of special plane curves, a paper on wallpaper groups, mathematics image gallery and links to software packages.

Mathematical Curves and Surfaces
Graphical representations of computer generated forms. (French/English).

Geometry from the Land of the Incas
Presents problems involving circles and triangles, with proofs, SAT practice quizzes and famous quotes. Also, has examples of geometry in Peruvian culture.

The Entropy Reduction Laboratory by Karl-Dietrich Neubert
Discusses double shell structured periodic systems, platonic spheres, molecular and crystal structures, and FlashSort algorithms.

Conjectures Produced by the Program Graffiti
Graffiti is a computer program that makes conjectures in mathematics and chemistry. Links to the conjectures and bibliography.

Geometric Group Theory
Information and resources about geometric group theory and low-dimensional topology. People, groups, meetings, links.

Encyclopedia of Triangle Centers
By Clark Kimberling. Over 1000 triangle centres in a searchable compilation with diagrams.

Math Forum: Geometry POW/POM Search
Search the Geometry Problem of the Week's archive of creative, non-routine challenges, as well as submissions and commentary, dating back to 1993.

Geometry Center
Web site for the (now closed) Center for the Computation and Visualization of Geometric Structures at the University of Minnesota. Graphics, multimedia, software, teaching resources.

Geometry Formulas and Facts
Excerpts from the 30th Edition of the CRC Standard Mathematical Tables and Formulas (1995), namely, the geometry section minus differential geometry.

Geometry and the Imagination in Minneapolis
Geometry exercises for a two-week summer workshop led by John Conway, Peter Doyle, Jane Gilman and Bill Thurston at the Geometry Center in Minneapolis, June 1991.

A Gallery of Interactive On-Line Geometry
At the Geometry Center.

The Kepler Conjecture
Information on the recent proof of Kepler conjecture on sphere packings.

Math Forum: geometry-research
Geometry professors and instructors may keep informed of the latest research conducted in their field at the geometry-research discussion list.

Fundamentals of Geometry
Free online book on geometry in pdf format. Contains material not easily found elsewhere from detailed exposition of elementary absolute geometry based on Hilbert's axioms to more advanced topics.

A New Way to Calculate a Triangle's Area
Using the length of the three sides. The proof is better understood than the old one.