REFERENCE

 Find it Now at the Math.com Library
  • Formulas - Formulas for all occasions. (English/Español)
  • Graphing and Plotting - See your graphs instantly!
  • Dictionaries - Math words defined.
  • Encyclopedias - longer articles
  • Math History - What happened when
  • Biography and Quotes - Famous mathematicians and more.
  • Science Fair Time - Plans and ideas for math projects. (Math Forum)
 Dictionaries
Glossary of Math Terms - (K-8) from Harcourt School Publishers.
English-Spanish Math Translation - Math terms translated from English to Spanish.
Measurement Dictionary - Dictionary of measurement terms by the Center for Mathematics and Science Education University of North Carolina at Chapel Hill.
Origins of Math Words - The history of mathematical terms. (Pat Ballew)
 Encyclopedias
Mathematical Atlas - (High School +) Definitions of the fields that make up mathematics. (Dave Rusin)

 Math History
Math History - The MacTutor History of Mathematics Archive offers a wide variety of topics related to math history: articles, explanations of math areas, biographies of mathematicians, information on Math societies, famous math quotations, and more.
Math History (Elementary - Middle School) Includes stories, inventions and biographies. This site from a Thinkquest team offers concise information and many pictures.
Famous Problems in the History of Math - This site presents a view of math history by studying some of the great problems that have inspired mathematicians throughout the ages. (Math Forum, Isaac Reed)