Favorite mathematics reference materials

Pspxworld.com maintains a list of mathematics text books available free online.

Mkaz.com, MathOpenRef.com, and FrontierNet.net all provide Javascript programs for graphing linear equations.

And my favorite, VisualStatistics.net provides extremely well structured tutorials in all things relating to statistical analysis as well as tutorials on the use of SPSS (the leading software package for statistical analysis)

And to answer your question, yes, I am the sort of person that keeps these kinds of links in my Favorites folder.