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!