European Mathematical Information Server (EMIS)
www.emis.de
(Euler project, preprints, Math Database (Zbl entries, demo version) and many others math goodies.


The Electronic Library of Mathematics
http://www.maths.soton.ac.uk/EMIS/ELibM.html
Provided as part of the European Mathematical Society's European Mathematics Information Service this site offers free access to electronic material including journals, proceedings, monographs, lecture notes, and graphical works. Articles are available in HTML, PostScript and PDF formats. Journals include Advances in Geometry, Discrete Mathematics & Theoretical Computer Science, The Electronic Journal of Combinatorics, The Electronic Journal of Differential Equations, The Electronic Journal of Linear Algebra, Electronic Journal of Probability and Electronic Communications in Probability, and Theory and Applications of Categories. Classical works include papers of Sir William Rowan Hamilton and Georg Friedrich Bernhard Riemann. There are many mirror sites (above is the UK one) and a list of additions and changes is available along with the criteria for inclusion.

MathGate provides the mathematics section of EEVL - the Internet Guide to Engineering, Mathematics and Computing. According to the Guardian, MathGate "...allows users to search thousands of quality assured maths resources" http://education.guardian.co.uk/higher/links/mathematics
Greig Fratus
MathGate Manager
http://www.mathgate.ac.uk/

Addison-Wesley has launched new online calculus tutorials and testing
http://www.mathxl.com/login.htm
Online indefinite integration
http://www.integrals.com
Database of maths definitions and knowledge (also now, other sciences)
http://www.mathworld.com
A fantastic archve of History of Mathematics - do not miss!!

TURNBULL is run by the School of Mathematics and Statistics at the University of St Andrews, St Andrews, Fife, Scotland.

TURNBULL is the home of the award-winning MacTutor History of Mathematics Archive -- an integrated collection of over 1000 biographies and historical articles of a mathematical nature, alongside interactive birthplace maps and the famous curve applet. To visit the archive click on the logo, name or here.

http://www-history.mcs.st-andrews.ac.uk/history/index.html

Lots of calculations related to the physics of cycling
http://www.analyticcycling.com/
Optical physics calculations
http://wyant.optics.arizona.edu/math.htm
Chemical engineering calculations
http://www.higgins.ucdavis.edu/webmath.php
An interactive exploration of the differences between the simple, small-angle, physical, non-small-angle pendula, along with various considerations of real physical behavior, for Edgar Poe's Pendulum
http://www.shodor.org/master/pendulum

Modellus™ Experiments with mathematical models - extremely interesting and useful
http://phoenix.sce.fct.unl.pt/modellus/
Contains also collections of examples for physics and mathematics!

The Comprehensive TeX Archive
ftp.dante.de
The MiKTeX Distribution of TeX (Windows)
www.miktex.org