Encyclopedia of Triangle Centres 
Clark Kimberling's definitive site.This now has almost 2500 centres. With full details of the centres and useful background information.

Edward Brisse's Lists  Invaluable lists of centres, and objects, such as lines and conics containing triangle centres.

Quim Castellsaguer's Site  Much useful information, with definitions anf theorems. Also has Cabri macros to plot centres and illustrate results.

Darij Grinberg's Site  Links to some of the author's many contributions to the subject of triangle centres.

Paul Yiu's Triangle Centres  A link to a postscript file (of 147 pages) giving a very good introduction to triangle centres and associated geometry.

Paul Yiu's Barycentric Coordinates  A brief but excellent introduction to barycentric coordinates.

Hyacinthos Newsgroup  A Yahoogroup devoted to the geometry of the triangle, with special emphasis on tringle centres. Note. My experience is that many mail agents "lose" some Yahoo messages. An effective remedy is to obtain a (free) Yahoo account.

MathWorld  This general mathematical site has many references to triangle geometry and triangle centres.
