Linux kernel hacker Benjamin Herrenschmidt recently posted on the debian-ppc mailing list a patch that finally permits sleep on Aluminium PowerBooks.
The patch (you can get it here or mirrored here thanks to gentoo guys) is in test stage and will work just for Al PowerBooks with an ATI graphic device. iBook support should come, sooner or later, Herrenschmidt is working on the video wake-up code. nVidia graphics based, instead, are for the moment left out of the games.Patch applies to 2.6.x kernels.

Another badly desired feature has been added. Sleeping is usually called suspend-to-ram, as opposed to suspend-to-disk mechanism that at the moment is known to work well but is clearly not that flexible and comfortable.