Quality of design and originality of analysis were primary factors in the selection process. A nice feature in some cases is the use of Mathematica on site. This eliminates the need for having the proper version of this software already available or the time-consuming process of downloading that version before using the tools available at the site. It is indexed by topics from pre-calculus through multivariable calculus.
Some sites provide practice final examinations.
A peek at such materials should convince our students that the standards we hold are universal. And tutorials are available for the first-year calculus student who is in need of a solid review of precalculus materials. There is a WWW site in the process of development which will provide case study modules relating to the study of calculus. Also included in this site will be discovery project sections, described as ways to stretch and explore concept knowledge. Another feature at some sites is access to excerpts from a collection of graphical demonstrations developed for first year calculus students.