Ministerio de Educacion, Cultura y Deporte (Spain)
La Historia De Matematicas a Traves De Los Siglos
In Spanish. Offers brief mathematical histories beginning with Egypt and Babylon up through the 19th century.
University of St. Andrews (UK)
University of St. Andrews: Non Euclidean Geometry
The University of St. Andrews in Scotland provides an excellent site explaining Non-Euclidean geometry.
University of St. Andrews (UK)
University of St. Andrews: Mac Tutor History of Mathematics Archive
The University of St. Andrews, Scotland, presents hundreds of biographies of famous mathematicians, histories of math in various cultures, and interesting facts on the development of important math concepts. This is a huge reference....