The Exchange on Drug Demand Reduction Action (EDDRA) is part of the European Monitoring Centre for Drugs and Drug Addiction's (EMCDDA) website. EDDRA provides details on a wide range of evaluated prevention, treatment and harm reduction interventions, as well as interventions within the criminal justice system, throughout Europe. A key aim of EDDRA is to encourage the exchange of information between intervention planners, project managers, etc.
You can access EDDRA here: http://www.emcdda.europa.eu/themes/best-practice/examples
Note that all questions are optional and all responses are collected anonymously.