A site at the University of Tennessee at Martin includes some pages on graph theory, including a tutorial on Euler and Hamiltonian circuits. It includes an interesting story on the origin of the phrase `Hamiltonian circuit'.

An explanation (using too much mathematical notation?) of minimal spanning trees (I'm looking for a better one..)

Another page on minimal spanning trees...still too much math...

A page about greedy algorithms, e.g., Kruskal's algorithm; again, a bit too much notation...

A page running a little Java applet that draws the minimal spaning tree for any collection of vertices that you put down - very cute!

A page (with Java applet implementation) that describes a method called simulated annealing for finding a short Hamiltonian circuit between collectionws of randomly chosen vertices.

A page describing a (sort of ) efficient algorithm for finding shortest Hamiltonian cicrcuits for a small (though important) collection of graphs, and its application to efficient circuit board design!

This page will let you flip up to 100 coins at a time, and observe the results!

A site called SOS Math at the Univ. of Texas at El Paso offers pages of material on topics ranging from polynomial long division, the quadratic formula, and trigonometric identities, to Taylor polynomials, the Cauchy-Riemann equations, and Matrix algebra.
Another site covering similar material, including solved homework problems for you to practice on, is kept in Belgium.

Dan Sloughter has a web page containing Java programs for visualizing various mathematical concepts. My favorite is one which will draw the Taylor polynomial approximations for y=sin(x) .

Forget a geometry formula? Check this page at Trinity College.

A Java-enabled page for generating Pascal's triangle (or rather, the last two digits of each entry, which is good enough through the 24th line). What's the pattern of the even numbers in the triangle?!