The Scratch folks are porting it to OLPC.
What is Scratch
Scratch is a highly engaging language that allows young students to create simple programs and games. Students use a drag and drop interface of "code blocks" to create sound, movement and actions to objects called "sprites."
A teacher writes: My 6th grade students enjoyed using Scratch. The Scratch website is well designed with both video and written tutorials. My students were especially pleased to be able to upload their completed projects directly to the Scratch Page. This gave the children a much larger audience than they would have gotten simply uploading to our classroom wiki page.
The Scratch team is currently working on an XO version of Scratch. The initial version has little integration with the XO and some of the features do not yet work on the XO, including the "note" and "drum" blocks and support for the Scratch Sensor Board. Better integration with the XO will be added incrementally.
If you have feedback about the XO version of Scratch, please write to scratch-xo at media mit edu (I've deliberately written that in a form that I hope spam robots won't recognize as a valid address).