On-line handwriting recognition for mathematical formulas, generates LaTeX and MathML and can pass on the formula to Wolfram Alpha.

Interesting information about numbers, the Mandelbrot set, Video effects/screen savers and RIES, an inverse equation solver (you provide a solution and it generates equations).

MIT Photonic Bands (MPB) electromagnetic eigenmode solver Meep finite-difference time-domain simulations Harminv extraction of complex frequencies and amplitudes from time series libctl Scheme/Guile-based scripting of scientific code (used as the interface for MPB and Meep). h5utils visualization of HDF5 data files NLopt nonlinear optimization library implementing many different optimization algorithms Cubature code for adaptive multidimensional integration of vector-valued integrands via the Genz-Malik algorithm. Faddeeva_w code to compute the complex error function (Faddeeva function).

Pancakes with interesting shapes. More can be found by following the links.

"Talk" by Ken Perlin about the use of noise in computer graphics.

How to create valid QR codes containing interesting pictures.

Citation of Brian Smith's work on the ZPOLY root-finding algorithm.
On 2022-07-25, the link points to the IMSL Numerical Libraries page. Does not matter, because I have found the document via http://portal.acm.org/citation.cfm?id=321615&dl=GUIDE&coll=&CFID=15151515&CFTOKEN=6184618 /add source/

A slide rule which can be used in a web browser.

XPP (XPPAUT is another name; I will use the two interchangeably) is a tool for solving * differential equations, * difference equations, * delay equations, * functional equations, * boundary value problems, and *stochastic equations.

Interesting information about analogue computers.