Assuming your running OSX on your iBook, you could use Target Disk mode.
Hold down the T key while you boot up the iBook. It will boot up as a firewire hard drive; the firewire symbol will apear on the screen. Connect the two with a firewire cable. The iBook drive will mount on your new Powerbook desktop. Copy the files as needed. This will be much faster if you have some really large files to copy.
Ben