What steps are taken to create the optical illusion "Autostereograms"?

I've known these previously as Single Image Random Dot Stereograms (SIRDS) or 3D Stereograms and if you are simply looking to create them rather than know the process (which Wikipedia will helpfully teach you about) then I've found a couple of options.

• Stereogram Creator is for Windows
• Easy Stereogram Generator is an online generator that will walk you through what is needed and can do it pretty quickly and easily
• SIRDS is a MAC OS X solution

The only program that can generate autostereograms I know of is a program called TIM. It's java, however I think the colors it uses is fairly ugly. However it is GPL so you may be able to use the source and edit it to a better pallet.