This is the concept I've been toying with for my next campaign:
Raise Dead works. The soul is returned to the body, somewhat resentful of its final reward being delayed. It wants nothing more than to return to the afterlife... but as with any summoning, it is compelled to complete one task specified at the time of the resurrection (generally -- complete the current adventure). If the character's body dies again before completing this task, the soul is destroyed forever -- meaning that to raise an ally is never to be undertaken lightly.
This offers several interesting possibilities. It allows the player of the dead character to essentially "finish out" the adventure, or, alternately, to set up a heroic sacrifice on his own terms -- not just because the Orc crit and rolled max damage with his greataxe. Best of all, in my eyes, character death is still meaningful because even though it can be held at bay temporarily, it cannot be staved off forever.
This also has the benefit of explaining why nobles and such don't have high level clerics on retainer.