Schafer, J.L. & Graham, J.W. (2002). Missing Data: Our View of the State of the Art. Psychological Methods, 7, 147-177.
This is a very well-written overview of the new approaches to dealing with missing data. Joe Schaefer is one of the top statististicians doing research on Missing data techniques and John Graham runs the statistical consulting center at Penn State. Together they explain these new techniques in understandable ways.