This interesting tutorial delves into a couple of different techniques for making holograms using your computer. There’s even an associated java program that can help you through the process

Creating a hologram is both fun and educational. There are quite a few good sites for learning about holography or purchasing supplies. As an alternative to the photochemistry and vibration-free settings involved with regular holography, this program allows you to create a transmission hologram using just a computer, a laser-printer, and an overhead transparency. This hologram will behave like one created using a laser and can be projected or viewed with a point source.

[Thanks, Chipwich!]