Use FireWire Target Disk Mode:
Connect the two with a FireWire cable, start the PowerBook while holding the T key. Its hard disk will mount and appear on the iMac's Desktop. Use iPhoto's File menu> Import to Library, and import its pictures.
Thanks for the info. I am off to an Apple Store to get the right Firewire cable today. Not sure which pin configuration I have, so going where I know I can get the right stuff. Then I'll try this work around. Hope I am right about the machine being in working order even 'tho the screen is disfunctional.
Depending on the age of your PowerBook G4, it could use either a FireWire 400 or FireWire 800 cable. All have FW800 but some have both. Your 2008 iMac will have FW800, so this cable will work:
It indicates availability in "1 to 2 months" but there are plenty of other sources for cables like it for < $10.
I will post my experience just in case someone else has this problem. John was right about the Firewire cable being the 800 9 pin job for both my PB G4 (2003 version) and my iMac (2008 version). Even though there was no screen to look at on the PB I was able to get into the target disk mode by first hooking up the firewire cable to my iMac and then the PB, then, holding down the "T" key on the PB I started it up. The iMac was already up and running.
It took several seconds but eventually a target disc icon for my PB showed up on the desktop of my iMac. Double clicking on the icon let me have access to all that was in the PB.
Sort of and here is where it got dicey. My PB and iMac do not run the same OSX versions, the PB being pretty old. Additionaly the cause of my concern was my wife's photos stored in some obscure location on the PB and using an old version of iPhoto which did not mesh at all with my iMac version.
After a bit of poking about and trying different work arounds I got lucky and a info box poped up saying that the data needed to be upgraded to be read by my newer version of iPhoto. Long storey short I went down this path and got everything transfered to the iMac. Just not sure how I got on that path, but I did.