I definitely liked the incarnate idea grep posted here
http://www.shatteredkingdoms.org/forums/viewtopic.php?f=22&t=20996&p=349636&hilit=incarnate#p349636.
I've also always like the idea of a shaman being able to seperate their spirit from their body. They could visit the Shores of Death while still alive, spy on others as an invisible ghost, and even mess around with others via poltergeist and limited chances to use some of their own spells on the living. Of course they could be exorcised and if someone happened along their body and killed them without their spirit inside of them, I'd imagine they could only come back through resurrection, and they'd still lose some experience, so jarring the process of dying without your spirit would be.
And in the spirit world they could attempt to possess a living body. Every action that would be attempted, even as simple as walking to the next room, would allow for a willpower save attempt and would exhaust some mental energy from the possessing spirit... I had more typed out at one point, but I'll just go back to wishful thinking.