Michael de Villiers
CUT THE KNOT at http://www.cut-the-knot.com
is an award winning site maintained by Alexander Bogomolny and contains delightful & stimulating geometry (& other) results. Most figures are interactive, and it also contains a forum for problem solving & mathematical results of interest.
ELEMENTARY TRIANGLE GEOMETRY at http://www.mfdabbs.com
Apart from algebra, trigonometry, statistics, etc. this site in the geometry section provides an exhaustive collection of simple to advanced geometry results related to the triangle, some trivial, some quite exotic. Downloadable in bookform, approx. 120 pp. (Also see http://www.mfdabbs.pwp.blueyonder.co.uk/index.html)
EUCLID'S ELEMENTS by David Joyce
GALLERY OF INTERACTIVE GEOMETRY at http://www.geom.umn.edu/apps/gallery.html
Practice and play with interactive software for building rainbows, projective conics, and many more.
THE GEOMETRY CENTER at http://www.geom.umn.edu/
The Center has a unified mathematics computing environment supporting math and
Computer science research, mathematical visualization, software development, application development, video animation production, and K16 math education. A good place to start to find other links, ideas, and resources!
GEOMETRY IN MOTION at http://www15.addr.com/~dscher
JavaSketchpad sketches with exciting problems, investigations & articles.
GEOMETRY JUNKYARD at http://www.ics.uci.edu/~eppstein/junkyard/
GEOMETRY STEP BY STEP FROM THE LAND OF THE INCAS at http://agutie.homestead.com Antonio Gutierrez's website provides stunning & delightful Dynamic Geometry sketches, animations, music, proofs, quotes, and much more.
DARIJ GRINBERG is a student whose homepage at http://de.geocities.com/darij_grinberg/
contains several unusual and new geometry results.
JAVASKETCHPAD GALLERY at http://www.keypress.com/sketchpad/java_gsp/gallery.html
The sketch gallery of the JavaSketchpad web-site. Some sketches are designed to be manipulated interactively; some are in the form of "push-button" demonstrations, and some are self-running animations.
JOHN SILVESTER'S HOMEPAGE
contains downloadable articles and Sketchpad sketches on geometry.
JOHN OLIVES HOMEPAGE at http://jwilson.coe.uga.edu/olive/welcome.html contains some useful & stimulating articles on teaching mathematics with Sketchpad and using other technology.
KIMBERLING'S TRIANGLE CENTERS presents over 400 different centers associated with the triangle at http://www2.evansville.edu/ck6/tcenters/ ranging from circumcenter, in center, nine-point center to more recently discovered ones some of which are quite exotic.
NONEUCLID is a Java software simulation offering straightedge and compass constructions in hyperbolic geometry at http://cs.unm.edu/~joel/NonEuclid/
MEETKUNDE by http://www.pandd.demon.nl/meetkunde.htm is n webwerf in Nederlands wat n nuttige ensiklopedie verskaf van interessante meetkundige resultate met bewyse, meesal toegelig met JavaCabri en/of aflaaibare Cabri sketse. (A website in Dutch that provides an encyclopedia of interesting geometry results with proofs, some illustrated with JavaCabri and/or downloadable Cabri sketches.)
PROJECTIVE GEOMETRY at http://www.anth.org.uk/NCT/
SYMMETRY & SHAPE OF SPACE
TEACHING & LEARNING GEOMETRY 11-19 at http://www.royalsoc.ac.uk
Summary of 2001 report of a Royal Society/Joint Mathematical Council Working Group.
The TOTALLY TESSELLATED site includes a large historical gallery of actual tessellations, illustrated and animated tutorials, information on M. C. Escher, an interactive gallery of user-submitted art, hands-on activities, and printable templates. Visit it at http://library.advanced.org/16661
TRIANGLE GEOMETRY http://www.onelist.com/community/Hyacinthos
WALTER WHITELEYS INTERESTING GEOMETRY SITES at
WEISSTEIN'S MATHWORLD - GEOMETRY
WIMS RULER & COMPASS