These are some programs I have written myself:

FractalJB - Explore the Mandelbrot Set fractal.

CryptographyJB - A utility to encrypt text.

2D to 3D - Manipulate a 2D image by rotating, translating and scaling in a 3D space.

Globe - Project a 2D image onto a sphere.

Platonic wireframes - View and manipulate (rotate, translate and scale) a tetrahedron, cube, dodecahedron and icosahedron.

Elapsed Days Calculator - Calculate the number of elapsed days between two dates.

Gravity Game - A simple game using Newton's laws of motion.

DOS programs - Take a trip back in time to the good old days of the Microsoft DOS operating system!