It's a story of a young girl named George who is killed in the pilot episode (via a freak accident) and becomes one of the "grim reapers". In every episode, George has to find people who are about to die (or become dead...like her), take their souls and guide them to the afterlife.
The show is now made into a movie (or direct to DVD?) and here's a first look at the trailer:
[Dead Like Me]