Rorschach Workbook for the Comprehensive System , Exner, J. (2000)
This is the essential beginner's guide to administration and scoring.

The Rorschach, Basic Foundations and Principles of Interpretation, Exner, J. (2002).  This is the newest text on history, administration, scoring, and interpretation.  Essentially, it is the first two volumes from the pervious (third) edition in one volume.  Excellent text I use to teach the course to graduate students.

Essentials of Rorschach ® Assessment. Rose, Maloney, Kaser-Boyd. (2000)
Very nice and concise work for people interested in having a "pocket" reference available.  Valuable addition to the entire "Essentials of Assessment" Series.

3 Volume Set of  "The Rorschach: A Comprehensive System", 3rd Edition, Exner, J. (1996).  The classic three volume set.  Volume 1:  History, Research, Foundations, Administration, and Scoring.  Volume 2: Interpretation with Adults.  Volume 3: Interpretation with Children and Adults.

Issues and Methods in Rorschach Research, Exner, et al. (1995).  More academic, but well worth the read if you are interested in the science behind the measure.  Part of the Lea Series in Personality and Clinical Psychology

Integrating the Rorschach and the MMPI-2 in Personality Assessment, Ganellen, Ronald. (1996).  This work is essential for any clinical psychologist or graduate student wrestling with the challenges of writing an integrative assessment that does not describe the patient on a "test-by-test" basis.  Also part of the Lea Series in Personality and Clinical Psychology.