Links

Other things you may find entertaining or useful:

• Computer-based constructions can be done using software such as Geometer's Sketchpad or Cinderella.
• A java-enhanced version of Euclid's Elements. Or, if you are impatient, you might prefer a quick trip through the Elements.
• A brief history of non-Euclidean geometry.
• Many proofs of the Pythagorean Theorem (84 last time I looked) from Cut-The-Knot, which has a lot of nice stuff on geometry.
• An interactive page with the four classical "centers" of a triangle (as well as the excenter and the Euler line). A much longer list of triangle centers can be found on Clark Kimberling's Triangle Centers page. He also has a number of nice animations.
• The nine-point circle.
• The Theorems of Menelaus and Ceva.