ValidationRegistry.cs

public class ValidationRegistry : Registry
    {
        public ValidationRegistry()
        {
            Scan(x =>
            {
                x.TheCallingAssembly();
                x.With(new ValidatorRegistrationConvention());
            });

            // Add the empty validator so that you don't have to manually create empty validators for entities
            // which have no rules
            For(typeof(IValidator<>))
                .LifecycleIs(InstanceScope.Singleton)
                .Use(typeof(EmptyValidator<>));
        }
    }

ValidatorRegistrationConvention.cs

using System;
using MuonLab.Validation;
using StructureMap.Configuration.DSL;
using StructureMap.Graph;
using StructureMap.TypeRules;

namespace StopSmokingWeb.Infrastructure.Validation
{
    public class ValidatorRegistrationConvention : IRegistrationConvention
    {
        public void Process(Type type, Registry registry)
        {
            var validatorTypes = type.FindInterfacesThatClose(typeof(IValidator<>));

            foreach (var validatorType in validatorTypes)
                registry.AddType(validatorType, type);
        }
    }
}