Geometry Center - University of Minnesota.

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

Math Forum - Geometry Problem of the Week - A weekly interactive project for geometry on the Internet.

http://mathforum.org/geopow/

Math Forum: K-12 Geometry - The best Internet resources for geometry: classroom materials, software, Internet projects, and public forums for discussion.

http://mathforum.org/geometry/k12.geometry.html

Geometry - Basic geometry terms and help. Brought to you by Math League Multimedia.

http://www.mathleague.com/help/geometry/geometry.htm

Mathematics Archives - Topics in Mathematics - Geometry

http://archives.math.utk.edu/topics/geometry.html

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

Building Blocks - Coordinate geometry - First Glance

http://www.math.com/school/subject3/lessons/S3U1L2GL.html

Arithmetic Tutorials, Tips: Algebra, calculus, geometry, math - Free lessons & tips for mathematics-related subjects: the basics, geometry, calculus, dealing with math anxiety and more.

http://www.knowledgehound.com/topics/math.htm

The Geometry Center - The Science U Geometry Center contains fun interactive exhibits, informative articles, and helpful lists of facts and formulas in geometry and related areas of mathematics.

http://www.scienceu.com/geometry/

Geometry Basics - Welcome to the Geometry portion of the site! 

http://library.thinkquest.org/20991/geo/index.html

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

http://faculty.evansville.edu/ck6/encyclopedia/

Geometry, Number Theory, and More - Math Lessons from Math Goodies.

http://www.mathgoodies.com/lessons/

Cut the Knot - Features articles about specific problems, illusions, and puzzles.

http://www.cut-the-knot.org/geometry.shtml

Geometry (Yahoo) - Yahoo! Mathematics > Geometry.

http://dir.yahoo.com/Science/Mathematics/Geometry/

Geometry Links (Eppstein)

http://www.ics.uci.edu/~eppstein/junkyard/topic.html

Geometry Resources

http://archives.math.utk.edu/topics/geometry.html

Geometry Formulas and Facts - Geometry Formulas and Facts.

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

Geometry & Topology

http://msp.warwick.ac.uk/gt/

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

http://www.geom.uiuc.edu/apps/gallery.html

Virtual Polyhedra - Encyclopedia of Polyhedra, with virtual reality models.

http://www.georgehart.com/virtual-polyhedra/vp.html