Get a Firewire cable. I think you'd need a 400-800 one because of the two different versions. Plug the two computers into each other with it. Then turn on the Powerbook while holding the letter T on the keyboard. After a few seconds, the hard drive should mount like a flash drive on the new Mac. You can copy data off this way.
Edit: Before you get rid of it, after all the data is copied, wipe the drive using Disk Utility on your new Mac. 🙂