Just stumbled across this article (with lots of feedback) about how to safe-sleep your mac (even desktop units), as long as you have OSX 10.4.3 and Open Firmware. The hack is a bit tricky (no GUI interface), but once enabled, saves all your ram to the hard drive on sleep, and restores from there on power-up. You can move desktop units this way, or go into extended "hibernate" during long periods of un-use for slightly better battery life.
Haven't personally tried it (I'm on the road and can't afford to make a mistake with my NVRAM :), but I'll give it a whirl soon.
