Cut the Knot
- Features articles about specific problems, illusions, and puzzles. Includes diagrams.
- http://www.cut-the-knot.org/geometry.shtml

Math Forum: Search geometry-forum
- Those interested in examining the previous incarnation of the Math Forum may search the archives of the Geometry Forum.
- http://mathforum.org/kb/forum.jspa?forumID=126

Mathematical Curves and Surfaces
- Graphical representations of computer generated forms. (French/English).
- http://perso.orange.fr/roger.assouly/

Math Forum: Geometry.research
- Discussion board for geometry professors and instructors to keep informed of the latest research.
- http://mathforum.org/kb/forum.jspa?forumID=130

New Mathematical Findings by Secondary Students
- High school students solve complex geometric problems by using GLad Sketchpad. Page includes diagrams.
- http://www.javeriana.edu.co/universitas_scientiarum/vol6n2/ART1.htm

Archimedes' Book of Lemmas
- A collection of all 15 propositions from Archimedes' Book of Lemmas with complete proofs, each accompanied by a Java illustration.
- http://www.cut-the-knot.org/Curriculum/Geometry/BookOfLemmas/index.shtml

The Lepidoptera of the Circles
- The Butterfly theorem and its generalizations illustrated by Java applets.
- http://www.cut-the-knot.org/ctk/Lepidoptera.shtml

The Complete Quadrilateral
- Several properties of the complete quadrilateral illustrated with Java applets
- http://www.cut-the-knot.org/ctk/CompleteQuadrilateral.shtml

NPR : Mathematicians Get Crafty with Geometry
- A husband and wife from Cornell University have come up with a crafty way to illustrate high-level geometry concepts -- by manipulating yarn into models that help explain the curvature of spaces. The mathemeticians talk with NPR's Jacki Lyden about hyperb
- http://www.npr.org/templates/story/story.php?storyId=4531695

GLaD Comments
- A new type of geometric construction that was discovered by Dan Litchfield and David Goldenheim. Includes general explanation and sketch examples.
- http://jwilson.coe.uga.edu/Texts.Folder/GLaD/GLaD.Comments.html

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.
- http://polly.phys.msu.ru/~belyaev/geometry.htm

The Kepler Conjecture
- Information on the recent proof of Kepler conjecture on sphere packings.
- http://www.math.pitt.edu/~thales/kepler98/

A Gallery of Interactive On-Line Geometry
- At the Geometry Center.
- http://www.geom.uiuc.edu/apps/gallery.html

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.
- http://www.geom.uiuc.edu/docs/doyle/mpls/handouts/handouts.html

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.
- http://www.geom.uiuc.edu/docs/reference/CRC-formulas/

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.
- http://www.geom.uiuc.edu/

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.
- http://mathforum.org/powgrepform.html

Encyclopedia of Triangle Centers
- By Clark Kimberling. Over 1000 triangle centres in a searchable compilation with diagrams.
- http://faculty.evansville.edu/ck6/encyclopedia/

Geometric Group Theory
- Information and resources about geometric group theory and low-dimensional topology. People, groups, meetings, links.
- http://www.math.ucsb.edu/~jon.mccammond/geogrouptheory/

Conjectures Produced by the Program Graffiti
- Graffiti is a computer program that makes conjectures in mathematics and chemistry. Links to the conjectures and bibliography.
- http://cms.dt.uh.edu/faculty/delavinae/research/wowref.htm

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

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.
- http://xahlee.org/PageTwo_dir/more.html

Geometry Activities
- By Ephraim Fithian.
- http://homepage.mac.com/efithian/geometry.html

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'.
- http://www.cut-the-knot.com/triangle/Morley/index.html

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.
- http://www.cut-the-knot.com/geometry.html

Cuboid and Cube Surface Distances
- A java applet with substantial analysis related to distances on a rectangular box.
- http://www.btinternet.com/~se16/js/cuboid.htm

Math 3210 - Higher Geometry I
- Course notes by Bill Cherowitzo.
- http://www-math.cudenver.edu/~wcherowi/courses/m3210/m3210.html

Packomania
- Includes packings of equal objects in containers together with source codes to obtain them numerically.
- http://hydra.nat.uni-magdeburg.de/packing/packing.html

Wilson Stothers' Inversive Geometry and CabriJava Pages
- Includes Steiner's Porism and the arbelos.
- http://www.maths.gla.ac.uk/~wilson/cabripages/inversive/inversive0.html

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.
- http://members.ozemail.com.au/~llan/

Bette Veteto's Homepage
- History of Mathematics, very strong on geometry.
- http://www.people.memphis.edu/~brveteto/

Tim Lister's Hyperbolic Geometry
- Cabri constructions for the demonstration of the basic concepts of hyperbolic geometry in the Poincare disc model.
- http://mcs.open.ac.uk/tcl2/nonE/nonE.html

Erich's Packing Center
- Graphics and links for various packing, tiling and covering problems.
- http://www.stetson.edu/~efriedma/packing.html

The Geometry Junkyard
- Usenet clippings, web pointers, lecture notes, research excerpts, papers, abstracts, programs, problems, and other stuff related to discrete and computational geometry.
- http://www.ics.uci.edu/~eppstein/junkyard/

Geometry in Action
- Includes collections from various areas in which ideas from discrete and computational geometry meet real world applications.
- http://www.ics.uci.edu/~eppstein/geom.html

Problem of the Minimum Rotation Surface
- Java applet demonstrating the catenary.
- http://home.ural.ru/~iagsoft/PMRS_J.html