just connect the 15" and the powermac with an ethernet cord, make sure Personal File Sharing is turned on on the powermac, and connect to the powermac from the powerbook using Cmd+K in finder (typing the computer's share name will be sufficient), then type in your shortname and password for the powermac in the prompt that comes up, then drag your applications and your home folder onto the powerbook's hdd. I wouldn't copy the OS because that stuff maybe newer than your old OS install on the powermac. Also your new shortname on the powerbook must match the shortname on the powermac if you want to use the home folder contents.
EDIT: I wouldn't use carbon copy cloner, since that copies the whole OS and you could run into problems.