Ars Technica has an in-depth look at a new version of the Sugar Learning Platform that can boot from a 1GB USB drive - hence the "stick".
The software environment was originally built for the One Laptop Per Child initiative for the XO laptop. It's a really kid-friendly computing interface pre-loaded with scores of education-related applications.
These drives could be distributed, and then children could plug them into whatever desktop computers were available at their location and enjoy their learning experience without regard to the hardware configuration.
Since the USB drive can save the user's data, the drive (and the learner's activity) would be portable, allowing the child to use it with any computer. What a great concept.
First taste: Sugar on a Stick learning platform