Update:
The Eighteenth International Conference on Principles and Practice of Constraint Programming is the annual conference on all aspects of computing with constraints, including:
theory, algorithms, environments, languages, models and systems, applications such as decision making, resource allocation, and agreement technologies.
The 18th edition will take place in Québec City, Canada from October 8th to October 12th 2012.
Find here a list of past CP conferences , or visit the Association for Constraint Programming.