Highly recommend getting a FireWire external drive and cloning your entire internal drive to it every so often. You can use the above-mentioned Carbon Copy Cloner or another utility called SuperDuper which is maybe a little nicer http://www.shirt-pocket.com/SuperDup...scription.html

The added benefit of cloning the entire drive (and using FireWire vs USB) is that the resulting backup can boot and run your PowerBook in the event of a failure of its internal drive, thus getting you immediately up and running with all your nomal stuff. The software mentioned above can clone the system even while it's running and produce a bootable backup.