Mirko wrote to me saying he got it to work using pegasos-dev-sources (there is currently no debian package for it) and the following patch. You can try to use a newer version patch.
More to come as soon as I will have taken time to get it to work here :D
It has been reported to work for a little time now, but for unknown reasons I am unable to test it now, shown below is an explanation by Florian:
Guido Guenther wrote a patch that make suspend to disk work for G4 iBooks. You should apply the patch before compiling the kernel using the command 'patch -p0 < pmdisk-2.6.5-rc3.diff'.
To be able to suspend you will also need to enable power management support (CONFIG_PM) and suspend-to-disk support (CONFIG_PM_DISK). It is also recommended to set the default resume partition (CONFIG_PM_DISK_PARTITION) to your swap partition (i.e. /dev/hda3) if you do not want to specify it via the bootloader or at the boot prompt.
After building and installing the kernel you should be able to suspend your system using 'echo -n disk >/sys/power/state'.
There are still some problems. You're recommended to unload some modules like therm_adt746x, ohci_hcd or some firewire related things. You should also disable DRI if you want your X-Server to suspend and wake up correctly without crashing the whole maching.