Update!
Balsa v 0.6 has been released, based on Ubuntu 9.04 Jaunty. See instructions and download here: Latest version
This will be the final Balsa version that can run on the OLPC XO-1.0.

Instructions for installing Balsa (Ubuntu 8.10 Intrepid, customised for language workers in remote parts of the world) have been moved. Find them under the "OLPC" menu item to the left, underneath the main Title, BALSA, on this page.
Or click here: Balsa on OLPC XO