UMass

U. Mass./Amherst Mathematics & Statistics Department home page.

Mathematica

Web site of Wolfram Research, publisher of Mathematica. Lots of information about Mathematica.

See, especially, the Wolfram Mathematica Learning Center, with its getting-started video screencasts, how-tos, and tutorials.

Instructive on-line Flash animations showing how Mathematica functions such as Map, Apply, Map, Partition, Sort, Flatten, Cases, etc., work may be viewed at http://documents.wolfram.com/flash.

Discrete math

Prime numbers: http://www.utm.edu/research/primes/

The Undergraduate Computational Engineering and Sciences Project module on public key encryption.

Interactive demo on how to multiply matrices (http://math.uww.edu/faculty/mcfarlat/matrixpj.htm)

“Everything” about math: Wolfram MathWorld (mathworld.wolfram.com)

“Everything else” about math: Wikipedia (en.wikipedia.org/wiki)

Find a good web site about discrete math?  Let me know and I’ll add a link to it here.

Miscellaneous

For fun (?):  http://users.chartertn.net/tonytemplin/FBI_eyes/index.html

For magic:  http://www.cyberglass.biz/flshstuff/mindreader.php